Most adults with a psychiatric diagnosis have a history of psychopathological disorders during childhood and/or adolescence (Kim-Cohen et al., 2003). The presence of psychopathological symptoms in childhood increases the odds of having a mental disorder in adolescence or early adulthood up to threefold (Copeland et al., 2013). Since psychopathology is a complex process that unfolds over time (Cicchetti, 1984; Sroufe and Rutter, 1984), describing its developmental course is vital from both a diagnostic and prognostic point of view. However, different risk or protective factors may modify psychopathological trajectories during different life stages. Developmental age is characterized by multiple transformations involving several neurobiological changes, and numerous new acquisitions and tasks. These transformations shape both the emergent personality patterns and the overall symptomatic manifestations of individuals. Therefore, psychological functioning during childhood or adolescence requires a careful and complex assessment and a thorough understanding of its underlying dynamics. Such assessment must always consider how each diagnosis evolves over time, the modifications in symptoms expression linked to neurobiological changes, and the clinical manifestations associated with each specific life phase.

The parent–child relationship is an additional aspect that requires careful evaluation as it can function as either a protective or risk factor for development. Particularly, attachment – which forms the foundation for the ongoing patterns of development – plays a crucial role in this regard. Although not directly associated with psychopathology, it can trigger developmental processes that, when examined, contribute to a more thorough understanding of the continuity of disorders.

We conducted a detailed search of the published literature with a review of the PsycINFO Record and Medline (PubMed) databases. Articles were included in the review based on the following criteria: (1) publication between January 1970 and October 2022; (2) being written English language. For our purposes, we used various combinations of the following keywords: “continuity,” “psychopathology,” “infancy,” “childhood,” “adolescence,” “adulthood,” “homotypic,” “heterotypic.” Articles were excluded if exclusively focused on epidemiologic data and if not specifically addressing the topic of psychopathology continuity. This exclusion criterion was chosen because a review on prevalence rates of psychiatric disorders across developmental periods has been already published (Costello et al., 2011).

A first search was performed to identify articles specifically focused on homotypic and heterotypic continuity. A second search was conducted to extract records containing a source of information (i.e., data, models, or hypotheses) on topics that are conceptually related to continuity of psychopathology (in particular, attachment). Finally, we considered cross-references and other review articles reported in the papers previously collected.

All articles cited in this manuscript were judged by the Authors to be relevant and to meet the scientific and conceptual criteria listed.

The literature search resulted in a pool of 36 longitudinal studies and other 190 articles covering the published research between 1970 and 2022.

Continuity of internalizing symptoms from early childhood to later ages has been extensively demonstrated (Briggs-Gowan et al., 2006; Snyder et al., 2017; Monk et al., 2021). Children with internalizing symptoms appear behaviorally inhibited, withdrawn, and prone to anxiety, depression, and somatic complaints. Internalizing disorders have been defined as based on “overcontrolled” symptoms (Kovacs and Devlin, 1998), indicating that they are inner-directed and linked to the attempt to preserve an excessive or maladaptive control of one’s states. A significant heterogeneity of symptoms across studies has been found (Tandon et al., 2009). Continuity patterns of internalizing disorders are summarized in Table 1.

Externalizing disorders define a wide range of aggressive and disruptive outward-directed behaviors (Campbell et al., 2000), such as oppositional defiant disorders (ODD), attention-deficit/hyperactivity disorder (ADHD), conduct disorder (CD), and substance-related and addictive disorders (Greenspan and Wieder, 2006; American Psychiatric Association, 2013).

Continuity patterns of externalizing disorders are shown in Table 2.

Children with externalizing problems are at increased risk for juvenile delinquency, academic failure, and social maladjustment (King et al., 2004; Englund and Siebenbruner, 2012; Basten et al., 2016); more generally, externalizing problems in childhood predict future psychopathology (Egeland et al., 1996; Campbell et al., 2000; Hofstra et al., 2002). The presence of high levels of hyperactivity-impulsivity, non-compliance, physical aggression, and other externalizing behaviors can be detected from a very early age (Mesman et al., 2001; Lorber et al., 2015; Carbonneau et al., 2016; Biedzio and Wakschlag, 2018; Wiggins et al., 2018), and these tend to remain consistent during development, creating patterns of both heterotypic and homotypic continuity.

To better comprehend the continuity of externalizing disorders, Copeland et al. (2013) have conducted a meta-analysis using data from various longitudinal studies – namely, the Great Smoky Mountains Study (Costello et al., 1996), the Christchurch Health and Development Study (Fergusson et al., 1989) and the Dunedin Multidisciplinary Health and Development Study (Silva, 1990). They found that externalizing disorders tend to be more stable and to present higher homotypic transitions than internalizing disorders, confirming the results of several other studies (Graham and Rutter, 1973; Offord et al., 1992; Achenbach et al., 1995; Pine et al., 1998; Ferdinand et al., 2007). CD seems to possess a stable homotypic trajectory from pre-school to adolescence (Gaffrey et al., 2018). ADHD and ODD show a robust homotypic pattern from childhood to adolescence (Finsaas et al., 2018; Obsuth et al., 2020).

ODD is a predictor of CD during adolescence (Lahey et al., 2002a), and both ODD and CD during childhood predict ADHD during teenage years (Wichstrøm et al., 2017). A recent study showed that the course of ADHD is highly heterogeneous; its trajectory is mediated by the severity of symptoms in childhood, risk for depression, medication use, IQ levels, comorbidities, and functional impairment (Vos et al., 2021). Other authors have found that ADHD during childhood remains a significant predictor for later ODD (Costello et al., 2003) and antisocial disorder (Mannuzza et al., 2004). Furthermore, research has shown that the relationship between ODD and CD may be bidirectional, as ODD symptoms are significant predictors of CD symptoms, and the latter predict ODD symptoms (Lahey et al., 2002a; Burke et al., 2005). A sub-analysis from the Developmental Trends Study (Burke et al., 2005), in which 177 boys were followed-up yearly until age 18, revealed that ADHD is a significant predictor of ODD. Homotypic and heterotypic continuity patterns were observed with depression, overanxious disorder, ADHD, ODD, and CD (ibidem). The authors (Burke et al., 2005) argued that ODD symptoms are related to the presence of temperamental and/or interpersonal difficulties and emerging aspects of antisocial personality traits, while CD symptoms reflect behavioral control problems.

CD and ADHD are significant precursors of both substance abuse disorder in adolescence (Disney et al., 1999; Costello et al., 2003) and antisocial personality disorder (Biederman et al., 1996; Patterson et al., 2000; Rutter et al., 2006; Copeland et al., 2009). In addition, externalizing psychopathology is a predictor of early alcohol, nicotine, and cannabis consumption, as well as of regular experience with these substances (King et al., 2004). Reviewing the results of seven North American controlled prospective longitudinal studies, Cherkasova et al. (2021) found that children with ADHD show significant difficulties in school and occupational functioning and significantly lower mental and physical well-being levels. They also present higher rates of substance abuse, antisocial behavior, and other risk-taking behaviors, including suicide attempts. Overall, the majority (84%) of children with persistent ADHD also had a comorbid disorder by young adulthood, with more than half of them having two or more comorbidities (Cherkasova et al., 2021).

Continuity between externalizing disorders can be better understood by looking at the presence of dysregulated patterns (altered control of attention, emotion, impulse, and arousal). The role of the lack of emotional and behavioral regulation plays a significant role in aggression, defiance, delinquency, and substance abuse behaviors (Eisenberg et al., 2010). Some authors (Beauchaine and McNulty, 2013) have proposed that ADHD, ODD, CD, substance abuse, and antisocial personality disorder have a common matrix, resulting from complex longitudinal transactions between interdependent individual vulnerabilities (e.g., genetic, epigenetic, temperamental) and contextual risk factors (e.g., experiences within the caregiving system and the peer group). Other authors (Wakschlag et al., 2018) have proposed that externalizing behaviors can be considered a neurodevelopmental syndrome that remains stable across the lifespan. Twin and family studies have shown that externalizing disorders can be conceptualized as a single continuous dimension of vulnerability in which hereditary factors play a significant role (Schmitz and Mrazek, 2001; Krueger, 2002; Kendler et al., 2003; Hicks et al., 2004; Blonigen et al., 2005; Bornovalova et al., 2010). A longitudinal study has demonstrated that the developmental trajectory of externalizing disorder is influenced by a wide array of factors, regarding both hereditary and environmental influences (Petersen et al., 2015), which supports the hypothesis proposed by Beauchaine and McNulty’s (2013) hypothesis. However, further research is needed to clarify the interplay between externalizing disorders and whether a common causal link may explain the observed continuity patterns.

There are also cross-predictions between internalizing and externalizing disorders (Costello et al., 2003). For example, the presence of a conduct disorder during childhood is predictive of anxiety and depression in adolescence (Graham and Rutter, 1973; Capaldi, 1992; Offord et al., 1992; Lahey et al., 2002a,b; Rutter et al., 2006). ODD during childhood is predictive of anxiety and depressive symptoms both in adolescence (Burke et al., 2005) and in adulthood (Kim-Cohen et al., 2003; Copeland et al., 2009), while ADHD during pre-school age is predictive of internalizing disorders during both school-age years (Wichstrøm et al., 2017) and adolescence (Shevlin et al., 2017). High levels of externalizing behaviors during childhood are predictive of internalizing symptoms later in life; changes in the symptomatology of one of the domains (externalization or internalization) often correspond to changes in the other (Gilliom and Shaw, 2004). Pesenti-Gritti et al. (2008) have found that high levels of externalizing symptoms predict subsequent co-existing internalizing problems in children.

Similarly, childhood anxiety and depression predict the development of externalizing symptoms. Anxious disorders during childhood are in heterotypic continuity with both conduct disorders (Costello et al., 2003; Bittner et al., 2007) and substance disorders (Huizink et al., 2006) during both adolescence and adulthood. A 21-year longitudinal study of a birth cohort of 1,265 children (Fergusson and Woodward, 2002) demonstrated that depression was a risk factor for developing nicotine dependence, alcohol abuse, or dependence in teenage years. Such heterotypic patterns may be explained considering the more significant impact of social and relational factors (e.g., interactions with peers) in adolescence, which could drive teenagers to express their distress through externalization. Externalizing behaviors, however, follow a different trajectory in boys and girls. Boys show more physically aggressive behaviors, whereas girls tend to show indirect aggression (Côté et al., 2007; Marmorstein, 2007). All forms of depressive disorders during developmental age seem to be associated with heightened levels of anxiety, substance abuse disorders, risky/criminal behaviors, and poor social functioning in adulthood (Copeland et al., 2018). These associations persisted when accounting for childhood comorbidities (such as anxiety and conduct disorder) and adverse experiences (ibidem). A 24-year longitudinal study from the Zuid-Holland population-based study (Reef et al., 2009) examined continuity patterns of internalizing and externalizing symptoms in children and adolescents (4–16 years): childhood aggression, delinquent behavior, and anxious and/or depressive symptoms are the strongest predictive factors for adult psychopathology (see also Hofstra et al., 2000; Althoff et al., 2010), while attention problems alone are not predictive of later difficulties (Reef et al., 2009). In addition, other studies have shown that anxiety and subsequent depression increase the risk for antisocial behavior (De Graaf et al., 2003; Burke et al., 2005; Diamantopoulou et al., 2010).

More recently, a study (Papachristou and Flouri, 2020) has shown that children with severe and persistent externalizing problems were more likely to develop a depressive disorder in early adolescence. After controlling for comorbidity with other conditions, Costello et al. (2003) found that continuity patterns between CD and depression remained significant for girls but not for boys. However, another study (Maughan et al., 2004) found an opposite trend. There is evidence that CD predicts depression, while depression is not predictive of antisocial behavior (Rutter et al., 2006). CD was also found to predict depression during early adolescence (Capaldi, 1992). The interconnections between behavioral and affective disorders could be understood by referring to the “failure model” (Patterson and Capaldi, 1990; Capaldi, 1992). According to this model, conduct problems lead to higher levels of interpersonal conflict, rejection, lack of support, and poor skills development, increasing the risk of subsequent depression and other forms of severe psychopathology. Studies have confirmed that difficulties in social interactions significantly predict depression (Patterson and Stoolmiller, 1991) and that peer rejection mediates the relationship between aggression and depression (Panak and Garber, 1992; Keiley et al., 2000; Kiesner, 2002).

Other authors have proposed that continuity patterns between externalizing and internalizing disorders can be explained through a shared etiopathogenetic factor. Recent studies (Finsaas et al., 2018; Waldman et al., 2021), for instance, have stressed the role played by the “irritability” factor, which can be considered a common characteristic among CD, ODD, childhood depression, and some forms of anxiety disorders during development. According to this model, the genetic or constitutional factors that influence children’s irritability levels in early childhood also predispose them to anxiety and depression in adolescence and/or adulthood. Frost et al. (2019), instead, have found that cortisol patterns moderate the course of internalizing and externalizing patterns from early childhood to adolescence: a steeper cortisol decline at age nine is predictive of higher internalizing symptoms at age twelve, while a blunted cortisol decline at the same age predicts higher externalizing problems Another etiological mechanism for externalizing disorders can also be found in environmental influences, such as maternal psychopathology (Jobs et al., 2019).

In the last twenty years, dysregulation disorders (i.e., sleeping, eating, and sensory processing disorders) have received growing attention due to the importance of behavioral and sensory regulation for adjustment and well-being (Winsper et al., 2020). However, literature on the continuity of dysregulation disorders is still scarce. The few available data have provided interesting suggestions. Symptoms of dysregulations in various areas show a homotypic pattern, remaining stable from early childhood to pre-adolescence (Boomsma et al., 2006; Hemmi et al., 2011). For what concerns heterotypic continuity, a study (DeGangi et al., 2000) revealed that 95% of infants with moderate regulatory disorders develop subsequent motor, language, and cognitive disorders, as well as relational problems. In addition, there is growing evidence that sensory processing disorders in infancy predict behavioral and emotional problems in childhood (Degangi et al., 1993; DeGangi et al., 2000; Briggs-Gowan et al., 2006). Moreover, children with dysregulation disorders might have low self-efficacy and difficulties in developing a clear sense of identity (DeGangi, 2017) and are more at risk of developing both externalizing and internalizing disorders (Maestro et al., 2012) – particularly mood disorders, conduct disorders, substance abuse disorders and suicidal behaviors (Holtmann et al., 2011), as well as personality disorders (Halperin et al., 2011).

As for eating disorders (EDs), the few available longitudinal studies (Bryant-Waugh et al., 2010; Ammaniti et al., 2012; Lucarelli et al., 2018; Herle et al., 2020) have found a prevalence of homotypic continuity patterns from childhood to adolescence. During childhood, EDs tend to remain stable (Farrow and Blissett, 2012). Studies (Ammaniti et al., 2012) found that early anorexia is a risk factor for a subsequent diagnosis of anorexia nervosa as well as for anxiety, depression, and behavioral disturbances from infancy to childhood [see also (Lucarelli et al., 2018)]. Another longitudinal study (Kotler et al., 2001) found that bulimia during early adolescence was associated with a nine-fold increased risk for subsequent bulimia in late adolescence and a twenty-fold increased risk for bulimia nervosa in adulthood. Late adolescent bulimia nervosa was associated with a thirty-five-fold increase in risk for adult bulimia nervosa. Calam and Waller (1998) found that bulimic symptoms in early teenage years are a risk factor for subsequent bulimic behaviors, while restrictive symptoms predict later purging behaviors. Drive for thinness and body dissatisfaction, two core characteristics of EDs, show high homotypic continuity across development (Waszczuk et al., 2019). Instead, bulimia symptoms tend to be less stable and less correlated with the other two symptoms (ibidem). Herle et al. (2020) have recently shown that childhood overeating is a significant risk factor for adolescent binge eating disorder, while persistent undereating predicts anorexia nervosa in adolescent girls. Persistent picky eating is associated with greater anorexia nervosa risk in both girls and boys. Although the risk of developing an ED is created by a complex interplay between genetic, biological, psychological, and environmental factors, research has shown the presence of shared etiological pathways for EDs (Hilbert et al., 2014; Bakalar et al., 2015), as well as how EDs symptoms in early childhood and/or adolescence represent a significant risk for having an eating disorder later in life.

Both internalizing and externalizing disorders may represent significant precursors of personality disorders (Bernstein et al., 1996; Lewinsohn et al., 1997, 1999; Krueger, 2002).

Classic theories of personality have tried to resolve the dilemma of stability versus change in personality development. Some authors argued that predicting adult personality from childhood behaviors is not possible (Lewis, 1998). However, there is evidence that personality traits do originate early in life, with continuity patterns identified across childhood, adolescence, and adulthood (Caspi, 1998; Roberts and Del Vecchio, 2000), and that personality traits are often observed from an early developmental stage (Levy et al., 1999; Belsky et al., 2012; Fortunato et al., 2021, 2022a).

A longitudinal study that assessed the personality traits of 975 children from age three found that behavioral qualities observed during early childhood are linked to personality functioning at eighteen years old (Caspi and Silva, 1995) and twenty-six years old (Caspi et al., 2003). “Under-controlled” (i.e., irritable, impulsive) children maintain emotional liability traits in adulthood; “inhibited” children maintain over-controlled and non-assertive personality styles; “confident” and “well-adjusted” children become adults characterized by assertiveness and adaptive behaviors. Other studies found a correlation between impulsiveness in pre-school children, behavioral problems in school-age and antisocial behaviors in adolescence (Moffitt, 2003; Bergman et al., 2009; Calkins and Keane, 2009; Lahey and Waldman, 2017). In addition, behavioral disorders such as ADHD, ODD, and other conduct problems are related to antisocial behaviors; their presence represents a significant risk factor for developing disordered personality traits (Caye et al., 2016; Moffitt, 2018; Wertz et al., 2018). Withdrawal behaviors and shyness in early childhood are related to the presence of avoidant personality traits in adolescence (Eggum et al., 2009), and impulsive and externalizing behaviors during development predict the presence of a borderline personality disorder later in life (Stepp et al., 2012).

Other studies (Komsi et al., 2006) point out that temperament shows significant continuity from infancy to middle childhood. Although homotypic continuity in personality traits is most likely to be evident only after puberty, it is possible to assess the consistent developmental trajectories of some temperamental characteristics. Childhood mental disorders can be as stable as adult ones (Cohen et al., 1993; Putnam et al., 2008), and it is well known that the presence of a mental disorder during childhood increases the risk of showing a mental disorder in adolescence or young adulthood (Copeland et al., 2013). Although more research in this area is needed, the findings cited above support the hypothesis that personality disorders may originate from emerging maladaptive personality traits already evident in preschoolers. Moreover, research about non-pathological personality traits has found that the Big Five dimensions remain stable from childhood to adulthood (Shiner and Caspi, 2003). Such personality traits might become pathological due to transactional processes and the influence of environmental factors (van den Akker et al., 2016). Having a personality disorder in adolescence increases the risk of having the same personality disorder or other disorders in adulthood (Caspi, 1998; Kasen et al., 1999). Positive environmental experiences may reverse this trend (Kasen et al., 2009; Kasen and Cohen, 2009). A longitudinal study has shown that the presence of an MDD during childhood increases the odds of developing a dependent, antisocial, passive-aggressive, and histrionic personality disorder by more than 13, 10, 7, and 3 times, respectively (Kasen et al., 2001). This effect was independent of age, sex, socioeconomic status, the presence of adverse childhood experience, preexisting personality disorder in teenage years, and other childhood or adolescent mental disorders. The same study has also shown that the presence of a disruptive disorder during childhood increases the odds of developing a schizoid, narcissistic, and antisocial personality disorder (Kasen et al., 2001).

More longitudinal studies are needed to further investigate emerging personality patterns in childhood and how their evolution in adolescence and adulthood could lead to the development of personality disorders. However, some elements of continuity have already been found from childhood to adulthood (Fortunato and Speranza, 2018). Obsessive, depressive, and paranoid personality traits show homotypic continuity across the lifespan. Avoidant, dependent, borderline, histrionic, narcissistic, antisocial, schizotypal, and schizoid personality traits show heterotypic continuity patterns. These traits may partly overlap, and they can be difficult to distinguish in childhood; therefore, it is vital to shed light on personality functioning during childhood and develop assessment tools to capture its complex dynamics.

The importance of the caregiver-child relationship as a protective or risk factor for development is well-known in the literature (Cicchetti, 1984; Sroufe and Rutter, 1984; Emde and Sameroff, 1989; Carlson and Sroufe, 1995; Emde, 2018; Dollberg and Keren, 2020; Farina et al., 2020; Speranza et al., 2020; Quintigliano et al., 2021; Yirmiya et al., 2022; Quintigliano et al., 2023). It is thus essential to consider this relationship when investigating psychopathology continuity. Attachment deserves particular attention among the developmental processes believed to underlie the continuity of psychopathological patterns. Attachment patterns tend to remain stable from infancy through adulthood (Waters et al., 2000). They can promote adaptive strategies or lay the groundwork for maladaptive behaviors, which may lead to the development of mental health disorders (Ma, 2006). Therefore, researchers have investigated the role of insecure or disorganized attachment in atypical development and psychopathology. Longitudinal studies (Sroufe et al., 1999, 2010; Sroufe, 2005) have demonstrated that insecure or disorganized attachment patterns (particularly the latter) are a significant predictor of maladaptive behaviors.

Attachment research also highlighted correlations between insecure or disorganized attachment in infancy and global indices of psychopathology (Cassidy and Mohr, 2001). Specifically, attachment disorganization increases the likelihood of psychopathology in adolescence (Carlson, 1998; Brown and Wright, 2003), and it is related to both internalization and externalization disorders, as well as to other conditions such as personality disorders (Lorenzini and Fonagy, 2013) and dissociative phenomena (Ogawa et al., 1997).

It seems that the results concerning attachment and psychopathology cannot be easily compared, primarily due to differences in both conceptualization and assessment of attachment dimensions. Moreover, longitudinal studies in this area are scarce. In the following sections, we will review some research highlighting the role of attachment in psychopathology since we believe that considering attachment patterns as affective regulation strategies, it is possible to identify to what extent a minimizing (avoidant attachment) or amplifying (resistant attachment) strategy might contribute to symptomatic expression and its continuity across development (Dozier et al., 2008).

The reported patterns of continuity in psychopathology suggest the need for early detection of its first clinical signs in infancy to implement strategies targeted at intervention and prevention (Cicchetti, 1984). Unfortunately, most studies have investigated only scholar age, not focusing on infancy or pre-schoolers (Kasen and Cohen, 2009). Studies are also often limited to specific populations (e.g., white, middle class; Ruchkin and Schwab-Stone, 2003). Finally, although the presence of homotypic and heterotypic continuity patterns across the lifespan has been largely demonstrated, further investigation is needed to understand the mechanisms that produce and maintain these trajectories.

Mechanisms underlying heterotypic patterns are indeed still under debate. The reviewed literature suggests that a given disorder may increase the risk of developing another if they share a common vulnerability factor. On the other hand, heterotypic patterns might occur by chance––in this case, however, continuity between them would not have possessed such strong empirical foundations (Ferdinand et al., 2007). Associations between disorders may also be mediated by comorbidity. Indeed, some heterotypic patterns disappear when comorbidities are considered. For this reason, some authors argue that the actual prevalence of heterotypic continuity is inflated (Angold et al., 1999). Other authors (Costello et al., 2003; Cummings et al., 2014) have found that heterotypic continuity persists even when controlling for comorbidity. A longitudinal study (Lahey et al., 2014) has shown that heterotypic patterns persist even after correcting homotypic ones. Various studies have focused on the influence of genetic and neurobiological factors: although the role of genetics has been acknowledged by most models on continuity (Rutter et al., 2006), it seems to play a role as a risk or mediating factor (Sroufe, 2009). As noted by Caspi et al. (2003), since many psychological characteristics such as temperamental qualities or personality traits are strongly related to genetic influences, these have previously been considered as able to explain continuity patterns. Such influences explain primarily how individual differences originate; however, continuity also appears to be strongly influenced by environmental factors.

Although it has not been thoroughly investigated in this paper, it is essential to mention the role of sex and gender in continuity. Some studies have shown that the prevalence of psychopathological disorders in childhood does not differ between sexes (Costello et al., 2003). However, some differences between the two sexes are present during pre-adolescence (Costello et al., 2003; Copeland et al., 2013), when depression becomes more common among females. Moreover, girls are more likely to present eating and affective disorders, while boys are more likely to have conduct and substance disorders (Reinke and Ostrander, 2008). Also, depression is often comorbid with CD in girls and substance use in boys (Lahey et al., 2000). However, more studies are needed to clarify the role of sex and gender in explaining dimorphic manifestations and their underlying processes.

Furthermore, the construct of continuity has relevant implications for diagnosis. The data reviewed in this paper support the utility of adopting a dimensional approach to mental disorders classification, especially during development. We must consider a complex interweave of factors to fully understand each form of psychopathology and its evolution over time. Adopting a dimensional approach could help clinicians and researchers to bridge the gap between clinical complexity and the need for empirical and methodological validity (Lingiardi and McWilliams, 2015). Biological and genetic dispositions, emotional regulation patterns, and the quality of early relationships with caregivers are all elements that influence the individual’s psychological functioning ––reflected through and organized in personality–– and are therefore all factors that should take into consideration both in psychological assessment and in studies investigating developmental trajectories of psychopathology (Lingiardi and McWilliams, 2017). An important gap in this area is the one regarding personality traits and disorders from childhood to adulthood. Considering personality functioning more thoroughly will allow clinicians and researchers to understand how seemingly different behaviors, symptoms, and disorders can evolve during development. It is essential, for example, to consider how individuals respond to their mental sufferance, how they give meaning to what happens to them, and if they believe to possess some degree of agency over it – all factors that influence how pathology will develop over time. Early adverse experiences profoundly impact self-representations and the quality of intimate relationships over time (Speranza et al., 2021), thus influencing personality development (Fortunato and Speranza, 2018; Riccardi et al., 2020). At the same time, a constitutional vulnerability to psychopathology might be amplified by a lack of adequate support by caregivers in childhood. In the famous nature versus nurture debate, it is essential to remember how personality represents a fundamental mediating factor of psychopathology. Since personality functioning can heighten or reduce the effects of environmental experiences, it can shape the characteristics, course, and stability over time of mental suffering.

In conclusion, knowing the homotypic and heterotypic continuity trajectories of mental disorders and being able to conceptualize them within a dynamic and comprehensive assessment frame can help clinicians and researchers better understand how psychopathology manifests itself during development. Recognizing the developmental trajectories of different mental disorders allows us to recognize them from the first subclinical signs, as well as to hypothesize how they will develop over time. This process is essential both for prevention and intervention – and can significantly help us formulate clinical hypotheses on the etiopathogenetic mechanisms underlying various disorders.

AS: conceptualization and writing–review and editing. ML and IS: writing–original draft. AF: writing–review and editing. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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