Since 2001, more than 2.6 million United States service members have been deployed or served in support of conflicts in Iraq and Afghanistan. Of those, one in four experience posttraumatic stress disorder (PTSD; 1) and one in five experience traumatic brain injury (TBI; 2). Suicide rates among Army and Marine Corps personnel are double the national average (VA Suicide Prevention). Sleep disturbances, anger, hypervigilance, substance misuse, and chronic physical and mental health disorders are seen frequently in returning service members and tend to co-occur (2–4). Although evidence-based treatments exist, established outpatient treatments have not adequately met the needs of the veteran and military population due to high drop-out rates (5, 6) and difficulties accessing treatment (7, 8). One solution to these barriers has been the introduction of intensive or "massed" delivery of protocols for trauma-focused treatment (e.g., 9–11). The growing literature on massed treatments suggests reduced dropout rates (12, 13) and possibly improved treatment outcomes (13, 14).

Home Base is a Massachusetts-based nonprofit that provides free mental health services – including transportation, lodging, and meals – for military service members, veterans, and their families. The two-week Home Base Intensive Clinical Program (ICP), an intensive outpatient program, launched in 2015 to address treatment gaps for service members and veterans struggling with PTSD and TBI. Serving individuals from across the globe, the program compresses approximately seventy hours of care into two weeks (15). The program benefits from philanthropic support that enables program design that attracts participants into care and minimizes treatment barriers. Since inception, the program has served over 2,500 participants and has maintained a 94.60% completion rate. Veterans and service members served by Home Base are often affected by comorbid mental diagnoses, substance misuse, cognitive impairment, occupational difficulties, and/or marital and family stress. Accordingly, a comprehensive treatment team approach was designed to address these comorbidities in a supportive environment away from home stressors, while also providing external lodging at a hotel to offer increased autonomy. This treatment model aims to harness the camaraderie of shared experience, integrating individual and group skill-building activities to enhance resilience, self-care, and overall health and wellness.

The Home Base ICP has a multipronged recruitment strategy to reach active duty service members and veterans. These include: (1) veteran and military family outreach teams who regularly connect with regional military organizations and participate in community events (16); (2) engagement with partner sites and other benevolence organizations; (3) networking with local and national mental health organizations and clinics who serve military communities, as well as participation in relevant conferences; (4) advertisement through social media and the Home Base website; and (5) word-of-mouth referrals from program alumni. Over the years, Home Base staff have fostered partnerships with community organizations that represent underserved populations such as Native American, Hispanic, and women veterans, working closely with these collaborators to advise on enhancements to typical program structure that further reduce barriers to engagement (e.g., translation of materials into Spanish, offering all-female cohorts).

The admissions process begins with the prospective participant submitting a self-referral form and a reason for seeking services. Any service member or veteran seeking treatment for symptoms of PTSD, TBI, anxiety, depression, or prolonged grief is considered, regardless of service era, branch of service, discharge status, or deployment history. Relative psychosocial stability, including stable housing, is required to set participants up for continued success following program completion.

The prospective participant is contacted to schedule a screening that includes demographic information, military history, medical history, and clinical history to include current symptoms, risk concerns, substance use, a TBI screen, and current treatment. Pre-treatment measures, including the PTSD Checklist for DSM-5 (PCL-5; 17) and the Patient Health Questionnaire (PHQ-9; 18), as well as releases of information for past treatment or current providers, are then sent to the prospective participant.

Upon receipt, records are reviewed by both medical and psychological team members to (a) identify potential concerns that may impact care or require accommodation during the Home Base ICP; and (b) confirm assignment to a Mental Health, TBI, or Hybrid treatment track. If no concerns are identified during this process, the participant is contacted by a social worker to discuss scheduling. If concerns do arise, they are discussed within a multidisciplinary admissions team and the prospective participant is provided with treatment recommendations. Examples of possible concerns include serious medical impairment, cognitive impairment, and/or other psychiatric conditions requiring higher level of care. Individuals are not eligible for the program if they present with active symptoms of psychosis or mania, acute behavioral concerns that require resolution (e.g. recent arrests) and/or would disrupt the program milieu beyond what is expected for this population (e.g., recent instance of violence toward other patients or providers), suicide or homicide attempt within the last 90 days, psychiatric hospitalization within the last 30 days, or substance withdrawal risk requiring detoxification. Potential participants must also be willing to abstain from illicit substances and alcohol during the program. If a veteran or service member previously attended the program, repeating the program requires a review of adherence to previous discharge recommendations and rationale for the likelihood of a better outcome following a second course of treatment.

During the admissions process, the prospective participant is assigned to the Mental Health track, TBI track, or a Hybrid track based upon presenting symptoms, history of TBI, and treatment resource availability in the patient's community. For individuals who present with both mental health and TBI concerns, the following criteria are used to determine track assignment: (a) whether mental health or TBI predominantly impacts the patient's current functioning; (b) the individual's preference; (c) the individual's history of evaluation and care pertaining to each condition; and (d) the availability of local care resources in the patient's community. For example, if an individual has limited access to both mental health and TBI-related services, Hybrid track is often recommended to maximize mental health and cognitive health gains from our program and to inform treatment planning after the completion of our program. In summary, if an individual has primary needs, they are assigned to the appropriate track; if an individual has both mental health and TBI needs, they are assigned to the Hybrid track; if access to a specific mode of treatment (e.g. cognitive rehabilitation services) is limited, they may be assigned to the track that provides the mode of treatment lacking in the patient's community. And, if further assessment is needed to clarify track assignment, the prospective patient is offered a pre-program multiday evaluation by a Home Base team, which is described in further detail below.

The Home Base ICP model previously discussed by Harvey and colleagues (2019), has undergone rapid expansion since 2018, both in terms of number of participants served and in treatment options provided. See Table 1 for a summary of the key programmatic elements that have been added or modified since the original publication. The program uses a whole-health-based approach, staffed by a multidisciplinary team comprising psychiatrists, nurse practitioners, clinical psychologists, neuropsychologists, clinical social workers, speech language pathologists, nurses, physical medicine and rehabilitation (PMR) specialists, registered dieticians, integrative health providers, and peer-to-peer veteran and family support specialists. Participants are assigned to a primary Mental Health track (primarily PTSD, anxiety, and/or depression), TBI, or Hybrid MH-TBI track during the admissions process after identification of their current symptomatology, history of TBI, and primary presenting concerns. Upon arrival, they receive daily evidence-based individual therapy and skills-focused group therapies grounded in CBT approaches. Additionally, all participants are provided psychopharmacology and case management, and engage in health and wellness programming described herein. Additional consultation sessions are also available based on the participant's needs, and support person programming is offered for participants and their loved ones. Further, all programming is supported and informed by veteran peers on staff who serve as liaisons between participants and providers. See Table 2 for services provided by treatment track.

As described above, participants are assigned to the Mental Health track prior to arrival and complete a clinical interview and eight 60-minute sessions of daily individual therapy provided by a psychologist or clinical social worker. Given the growing evidence for the efficacy (10, 15, 19–21) and tolerability (11, 22, 23) of massed trauma-focused treatments, treatment primarily consists of Prolonged Exposure (PE) or Cognitive Processing Therapy (CPT), two of the gold-standard treatments for PTSD. In line with best practices, shared decision making helps to determine treatment intervention after completion of the clinical interview. Participants who present with psychiatric diagnoses other than PTSD (e.g., persistent complex bereavement disorder, major depressive disorder) often engage in other evidence-based treatment modalities, including Prolonged Grief Treatment (24), cognitive behavioral therapy, or an adaptation of the Unified Protocol (UP; 25) designed for the Home Base ICP in collaboration with the UP Institute.

Participants may be assigned to the TBI track at any time during the admissions process and, if indicated, undergo a pre-program multiday evaluation by a Home Base team including PMR, physical therapy, neuropsychology, psychiatry, and psychology. These evaluations provide treatment recommendations for the Home Base ICP, and treatment determinations are made through collaborative decision making with the participant. Potential outcomes include referral to one of the program tracks or to local providers.

Participants in the TBI track receive daily, 60-minute individual cognitive rehabilitation sessions administered by a licensed speech-language pathologist or neuropsychologist. Our cognitive rehabilitation model is based on cognitive compensation, which focuses on the use of internal and external strategies to support cognition (26). Individual session treatment goals are determined collaboratively, and participants practice compensatory strategies aimed at improving daily cognitive functioning. Additionally, participants are offered three to four vestibular physical therapy sessions, and consultation sessions with a PMR physician for care of medical symptoms such as headaches. Based on individual needs, participants may be referred to specialized evaluations (e.g. audiology, neuroendocrinology, sleep medicine, orthopedics).

Given the relationship between mental health conditions and TBI in military personnel (27), the Hybrid track was developed for participants who would benefit from engaging in services offered within both the TBI and mental health tracks. A meta-analysis has shown that cognitive rehabilitation is effective for improving memory in participants with PTSD (28); conversely, other studies have shown that PTSD treatments are effective regardless of the presence of TBI or its severity (29). Accordingly, a treatment plan may consist of a combination of vestibular therapy, individual psychological therapy, and PMR consultation to help address each patient's specific sequela.

All participants receive approximately 45 hours of group therapy. Groups include dialectical behavioral therapy (DBT; 30) skills, in vivo exposure adapted from PE (9), cognitive health, Resilient Warrior adapted from the Relaxation Response Resiliency Program (31, 32), substance use education, and process groups. This model was selected to facilitate group cohesion and to increase participants' healthy coping while participating in daily individual therapy (33). A sample group schedule is provided in Figure 1 .

DBT skills group target deficits in mindfulness, emotion regulation, distress tolerance, and interpersonal functioning commonly seen in PTSD and other emotional disorders (34, 35); in vivo exposures target avoidance that interferes with extinction learning and self-efficacy (36); and Resilient Warrior sessions target the development of coping skills for distress through mind-body techniques (37). Cognitive health and substance use education groups provide education and coping skills to address the cognitive impairments and substance use concerns commonly reported in military and veteran populations (38, 39).

Every participant is assigned a psychopharmacology provider (psychiatrist or psychiatric nurse practitioner). This plan may include psychoeducation, adjustments to existing medications, or non-pharmacologic interventions. Psychopharmacology providers adhere to treatment guidelines for PTSD, depression, and anxiety (e.g. 40), which do not support prescribing benzodiazepines. Participant preferences regarding medications are respected, with some willing to initiate pharmacotherapy, and others hesitant or opposed to due to stigma, side effects, potential negative implications to their military career, or prior medication trials. Psychopharmacology providers meet with participants as frequently as clinically indicated to address these concerns, make recommendations for ongoing care at home, answer questions, and collaborate with the participant's local treatment team.

Case management is provided to all participants, many of whom live out of state or far from large Veterans Affairs (VA) medical centers. A social work or nurse case manager works closely with each participant and their support person to ensure a smooth transition both into and out of the program. The case manager meets with the participant to assess and address psychosocial concerns (e.g., housing, financial stress) or treatment needs, and collaborates with support people and other providers to determine an individualized discharge plan. One month after completion, a resource specialist calls graduates of the program to assess needs and inquire about additional resource requests. Any responses that indicate that the individual is in need of resources are directed back to their Home Base ICP case manager for follow-up.

Through a Memorandum of Understanding (MOU) between Home Base and the VA, a VA social worker is embedded in Home Base to assist with records transfer, benefits support, and connection back to the VA upon program completion. This VA liaison meets with participants during the program to discuss any referrals made by Home Base to the participant's community VA Medical Center or Community Based Outpatient Clinic.

Substance use disorders (SUDs) are commonly comorbid with PTSD and TBI (42, 43), with some studies evincing a rate of around 50% (e.g. 44). Participants frequently request assistance with reducing or eliminating use; thus, the voluntary Dual Recovery (DR) supplement was launched in 2021 to increase access to, and successful completion of, the program for veterans and service members who are in early recovery or managing substance misuse. In addition to the standard program components, individuals experiencing substance misuse or behavioral addiction meet with a SUD or behavioral addiction clinician for an educational meeting the week prior to arrival, and for up to six additional individual therapy sessions. These sessions incorporate principles from Motivational Interviewing (45) and cognitive-behavioral strategies from the Concurrent Treatment of PTSD and Substance Use Disorders Using Prolonged Exposure (COPE; 46) protocol. A Recovery Coach is available to all participants during the program and provides caring contact emails to DR participants for one year following program completion. Further, DR participants are matched with medication providers trained in addiction medicine, who incorporate medications for substance use as clinically indicated. Commonly prescribed medications include FDA-approved medications for alcohol use disorder and nicotine use disorder. Gabapentin is also used to manage cannabis withdrawal symptoms. Although participants are not started on buprenorphine or methadone during the program, providers can support participants in continuing established treatment.

Individuals close to participants are often impacted by issues arising from their military service, reintegration, mental health concerns, and TBI symptoms. Limited resources are available for support people and there is limited expertise among community providers providing such services. Research has demonstrated that support persons can increase motivation for treatment (49) and reinforce treatment outcomes and adherence (50). Participants can invite a support person to participate in two days of educational programming. The program provides a supportive and validating environment for support people to share their own experiences and struggles while also indirectly supporting the participant's recovery.

Support people receive 11 hours of group-based programming, including psychoeducation covering PTSD, readjustment issues, cognitive health, substance use, and the impact of trauma on relationships, as well as overviews of programming (e.g., integrative wellness, DBT skills). Two conjoined participant-support virtual groups also offer opportunities to practice effective communication skills. Support people connect with social workers who offer case management resources for care in their community as needed.

Veteran Outreach Coordinators (VOCs) are veterans and service members who provide non-clinical peer support services to participants. They work closely with clinical leads to inform programmatic planning, provide insight into military culture, and ensure appropriate tailoring of the services to the participant population. VOCs actively listen to and advocate for participants throughout their treatment, aiming to promote a treatment milieu that offers psychological safety and mutual respect.

Consistent with established literature (51, 52), participants are more willing to speak to fellow veterans about their service and disclose uncomfortable matters to those with similar lived experience. This information allows for rapid response within the clinical team to better triage risk and treatment-related concerns, and to inform culturally sensitive treatment plans. VOCs aim to redefine veteran peer relationships for participants who may have had a difficult experience during their time in service. This connection aims to help veterans build long-lasting relationships within their community.

The VOC team oversees logistics for program arrivals, daily check-ins, and non-clinical evening and weekend programming. Non-clinical activities provide opportunities for participant cohesion, expansion of support networks, and practicing skills taught during clinical programming outside the clinical setting. Evening programming typically involves military history activities; weekend programming focuses on activities that foster communication skill development and time for decompression.

This report describes a two-week massed treatment program for veterans and active duty service members struggling with symptoms of PTSD, anxiety, depression, TBI, prolonged grief, and co-occurring substance use. Although a diagnosis of PTSD is not required for participation in the program, it is a primary concern reported by participants with 88% of all participants seeking evaluation or treatment for PTSD and 2.5% seeking evaluation or treatment for PTSD and TBI.

Consistent with prior literature (12), providing trauma-focused treatment via a massed protocol was effective in the long-term reduction of trauma-related symptomatology in veteran and military populations. Such a massed protocol has several advantages including a low dropout rate, as evinced by the overwhelming number of our participants completing the program. Consistent with established literature (9, 64), patients with PTSD and comorbid sequelae from TBI also benefited from trauma-focused care. Expectedly, these gains extended into other quality-of-life functioning (e.g., 65).

In an effort to better understand who may benefit from a massed protocol, and how the benefit is conferred, analyses investigated subsets of the data. Initial analyses indicated that demographic variables did not play a statistically significant role in treatment outcomes. Further analyses demonstrated statistically significant differences among the modality of individual therapy (i.e., UP vs. PE vs. CPT vs. general CBT). On one hand, these findings may indicate that depressive symptom cluster in patients seeking trauma-focused treatment may respond to evidence-based treatments for trauma such as PE or CPT, given the substantial overlap between PTSD and depression diagnostic criteria. On the other hand, these findings do not surpass the ten points change that the National Center for PTSD considers clinically significant, therefore extrapolation of their relevance beyond the statistical context should be tempered. Similarly the differences by time period (pre-, during- and post-COVID) need to be tempered as they meet the threshold for statistical significance but do not cross the clinically meaningful thresholds for the measures. While a component analysis is outside the scope of this manuscript, further investigation into the reduction of change scores over time is important to ensure that programmatic changes are having the desired and expected effects, particularly because this trend persists for several measures.

The expected effects were seen for the MH track providing greater benefits for PCL-5 and PROMIS Ability scores, but the conversely expected effects – NSI improving more for TBI track patients than MH patients was not evinced. Nor were, curiously, the differences in change score for symptoms of depression. This lack might be accounted for by the programming (i.e. Cognitive Health for NSI and wellness programming and/or DBT for PHQ-9) or the significant overlap among the measures' items and symptom clusters.

In line with extant findings (66) having a support individual engage with the adjunctive programming was associated with better symptom improvement over the course of the program. Interpreted conservatively, this finding could reflect the benefit of having strong social supports, measured here by the presence of an individual dedicated enough to one's recovery to commit to participate in psychoeducation and skills training for the benefit of the participant. More liberally, this finding could demonstrate some direct support for the burgeoning investigations (6) of benefit of supportive individuals in patients' trauma-focused treatment (50).

Given the high completion rate and strong outcome data, this model should be considered as an option for military service members struggling with symptoms that lead to lower functioning and poorer quality of life. Findings add to the emerging literature that massed treatments for trauma are well tolerated and show long-term benefits in this population (12).