Parkinson’s disease (PD) is a neurodegenerative disease characterized by both motor and non-motor dysfunction. The motor manifestations including rigor, tremor, postural instability, and freezing of gait are well described and commonly recognized (Shulman et al., 2002; Chaudhuri et al., 2006). The non-motor manifestations such as fatigue, apathy, depression, anxiety, and sleeplessness have recently attracted increased scientific interest and appear to have a greater impact on the quality of life (QoL) than the motor manifestations (Richard, 2005; Martinez-Martin, 2011).

Martínez-Martín (1998, pp. 2–6) defined the health-related QoL of patients with PD as “the perception and evaluation, by patients themselves, of the impact caused on their lives by the disease and its consequences.”

Depression (Weintraub et al., 2004; Martinez-Martin, 2011; Jones et al., 2015) and anxiety have been found to be associated with a low QoL (Jones et al., 2015). Soh et al. (2011) analyzed 29 articles that examined predictors of QoL in patients with PD. Besides motor symptoms, disease severity, and demographic variables, non-motor symptoms such as apathy, depression, and anxiety were found to predict QoL. Depression and anxiety are also negatively associated with the motor symptoms of PD (Dissanayaka et al., 2011) and the progression of the disease (Schrag et al., 2000; Leentjens et al., 2013).

Cognitive behavioral therapy (CBT) is an effective treatment for depression, anxiety, and phobias, in both individual and group therapy settings (Hofmann et al., 2012). Even in elderly patients (Peng et al., 2001; Ceri, 2007) and in patients with neurological diseases, positive effects such as a reduction of depressive symptoms have been reported (Mohr et al., 2001, 2004). Until now, studies have been focusing on the treatment of the non-motor symptoms such as depression and anxiety rather than the improvement of QoL. Dobkin et al. (2011) examined the impact of individual CBT on depression and anxiety on 80 patients with PD during 10 weeks. The control group only received four unspecific, short phone calls. Patients receiving CBT have shown significantly less symptoms of depression and anxiety than patients in the control group. This study has shown that individual CBT lessens depressive symptoms and anxiety in patients with PD. Patients have also reported an improvement of their QoL (Dobkin et al., 2011, 2012). A statistical analysis of QoL has not been assessed. Based on this study, Dobkin et al. (2012) discerned predictive factors of the effect of CBT on depression and anxiety. The inclusion of caregivers predicts the effect of the treatment (Dobkin et al., 2012). Considering the negative impact of non-motor symptoms on QoL, a focus on the improvement of QoL could be advantageous.

There have been only a few studies of the use of CBT to treat QoL and stress in patients with PD. A high stress level reinforces and establishes motor symptoms (Metz, 2007; Hemmerle et al., 2012). CBT aims to identify the stress level and modify negative cognitive beliefs and behaviors (Beck, 1979). Therefore it might yield greater improvement than drug treatment alone, and any type of effective treatment would be of considerable clinical significance in view of the high prevalence of PD (1–2%) (Moreno et al., 2013). Group CBT is more cost-effective and has similar effects as individual CBT (McDermut et al., 2001). In addition there is a lack of studies that use an active control group, which receives the same frequency of sessions. The health enhancement program (HEP) of MacCoon et al. (2012) has been developed for the purpose of building an active control intervention for a mindfulness based stress study. To fill these gaps in research, the present study examines a randomized, controlled trial of CBT for reducing stress and improving QoL in patients with PD, with HEP as a control intervention.

In this study, we examined whether cognitive behavioral group therapy lessens stress and improves QoL in PD patients more effectively than a HEP. We found that it does, and that the effect is mostly accounted for by a worsening of BELA and PDQ-39 scores in the control (HEP) group. Similar findings were seen on all subscales except for the communication and physical discomfort subscales of the PDQ-39, on which all patients showed a decline. These results are comparable to earlier findings: Tiihonen et al. (2008) analyzed the effect of group CBT versus no treatment in PD patients with PD and found that the CBT patients die significantly better in terms of QOL as assessed by the PDQ-39, the difference being accounted for by a worsened QoL in the control group.

When interpreting the findings of this and other trials involving PD patients, one must bear in mind the progressive nature of the disease. The control group received physiotherapy, music therapy, and dietary counseling. The CBT training was intended to improve the patients’ emotional and social skills, so that they would suffer less from stress due to the manifestations of PD and would achieve a higher QoL despite progression of the disease. Patients in the CBT group received training that was focused on coping with the disease the development of self-efficacy (belief in one’s own ability to perform tasks and reach goals). Previous studies have revealed that self-efficacy contributes to a high QoL and a low stress level (Tiihonen et al., 2008). We think the worsening QoL in the control (HEP) group of this study may well have been due in large part to these patients’ increased distress over their progressive physical limitations. The BELA consists of questions about the emotional burden resulting from a variety of problems (anxiety, etc.), rather than these problems themselves. As HEP is focused on physical training rather than emotional burden reduction, one may speculate that the patients in our control group may even have experienced the HEP training itself as stressful, which, in turn, may have contributed to or accounted for their lower BELA change score. Likewise, in the PDQ-39, many of the items whose frequency the patients are asked to estimate are themselves feelings, such as worry about other people’s reactions. In this case as well, HEP training is not specifically directed against such items and could conceivably even make them worse.

Both groups reported increased physical discomfort after training. This shows that the CBT group did not experience better physical well-being through the development of strategies to deal with the disease itself, and that the HEP intervention did not improve the physical manifestations of the disease sufficiently to improve physical comfort. Perhaps coping with the disease is more important than direct treatment of its manifestations. In one study, a higher optimism score was correlated with lesser severity of disease (Shifren, 1996), indicating that disease severity is influenced by the patient’s perception. It follows that a treatment focused on a change in attitude toward the disease could be beneficial.

This study also shows that younger patients with PD show a larger improvement in QoL after CBT than older patients. The older patients in this study had generally suffered from PD for a longer time (p = 0.026); the effect of disease duration as a predictor disappears in the regression model with age. Younger patients, who generally have had the disease for a shorter time and have more years left to live, may well be better motivated to cope with the disease than older ones. Stanley et al. (2009) reported in their study using CBT for treating general anxiety disorder (GAD), greater effect sizes in younger patients than in older ones. To minimize this effect, Laidlaw et al. (2008), developed CBT concept specifically for elderly patients. The authors suggested to focus on issues that are explicitly related to this age, such as physical health, role characteristics, losses and relationship to younger generations. Even though we did have age related issues in the CBT treatment of this study, they were not discussed deeper. Instead we focused on disease-related issues where patients learned to restructure the negative associations with the disease, (e.g., being ashamed of it).

CBT activates the prefrontal cortex that is responsible for the process and regulation of emotions (Goldapple et al., 2004). This effect can be applied to any patient; therefore it can be used for a variety of patient groups. The review article of (Berardelli et al., 2015) shows that previous studies examining movement disorders found a reduction of depressive symptoms and an increase of QoL after receiving CBT. In a study using CBT on patient’s with multiple sclerosis, patients have shown a better QoL after the treatment. This effect was mediated by depression (Cosio et al., 2011). These findings show, that CBT can generally have an impact on QoL in patient’s with physical diseases.

The small scale of this study limits the interpretation of its findings. Because of the small number of observations, MANOVA could not be applied to all variables, and ANOVA had to be used instead, yielding less detailed findings. If more patients had been included in this study, its findings would have been more robust.

Moreover, this study did not include either a group of healthy subjects without PD or a group of PD patients who did not receive any training at all. Either or both of these negative controls might have revealed general training effects that this study, as performed, could not address. For future studies, a larger number of observations as well as a group of healthy participants would be necessary to reveal well funded statements.

With these limitations, this study indicate the possibility that CBT lessened stress and improved QoL to a greater extent than HEP in – particularly younger – patients with PD. We conclude that group CBT might be a promising treatment for preventing increased stress and a declining QoL in patients with PD.

AH: analysis and interpretation of data, acquisition of data. AM: study design, acquisition of data, and interpretation of data. VB: acquisition of data, interpretation of data. FH: acquisition of data, critical revision of manuscript. KN: study design, acquisition of data, and interpretation of data. ET: contribution of core ideas, critical revision of manuscript for important intellectual content. EN: supervision, critical revision of manuscript. R-DS: study concept, critical revision of manuscript. PF: study concept, acquisition of data, and critical revision of manuscript. UG: study concept and design, acquisition of data, supervision.

ET has received research funding from the Swiss National Science Foundation and the Synapsis Foundation, Switzerland. FH received a grant from the Freiwillige Akademische Gesellschaft Basel. R-DS – received a grant form Vifor and serves on an Abvisory Board for Medicine. PF received grants from Parkinson Schweiz, the Jacques and Gloria Gossweiler Foundation, the Freiwillige Akademische Gesellschaft Basel, the Swiss National Science Foundation, the Hedwig Widmer Foundation, and unrestricted grants from Abbvie AG and General Electric. UG received grants from Parkinson Schweiz, the Jacques and Gloria Gossweiler Foundation, the Freiwillige Akademische Gesellschaft Basel, the Gottfried and Julia Bangerter-Rhyner Foundation, the Swiss National Science Foundation, the Camelia Botnar Foundation, and the Hedwig Widmer Foundation, and unrestricted grants from UCB Pharma AG, Abbvie AG, and General Electric.

All the other 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.