This case series and feasibility trial evaluated a novel integrated cognitive behavioral treatment, which was adapted specifically for homeless individuals and developed to treat substance use and depressive symptoms simultaneously. The integrated cognitive behavioral treatment was delivered among four homeless individuals enrolled in the Treatment First program (a social services program where treatment is offered in conjunction with temporary transitional housing), who had access to stable and sober housing milieus.

All study participants were clients at the social welfare office for the homeless, a specialized unit within the social services in Stockholm, Sweden. The participants were referred to outpatient treatment at Pelarbacken, a specialized primary care center for homeless patients.

The integrated cognitive behavioral treatment was developed as part of a collaborate treatment program between the social welfare office for the homeless and Pelarbacken. Post treatment interviews and individual behavioral analyses of prior patients showed that the far most common reason for alcohol or drug use, was coping with negative affect (46% reported this reason). The integrated cognitive behavioral treatment was developed emanating from the following analysis (1) being homeless often implicates having lost contact with several important life areas, substance use might be the only reinforcing activity left; (2) common reactions are stress and depressive symptoms, and avoidance based strategies such as passivity, isolation, avoidance of social contact, or substance use; (3) when decreasing substance use, a transient approximate 3 month period of increased "depression-like" symptoms occurs, which might lead to lapses or relapses (this period is also called post-acute abstinence, or protracted abstinence). The ICBT (5-15 sessions) was developed to extend over this time period, with the overall aim of participants to (1) access a stable, sober housing milieu, and decrease substance use; (2) learn strategies to cope with negative affect; and (3) learn strategies to cope with life changes, increase activities such as work, social contact, exercise or leisure activities.

Measures were administered at pre treatment, weekly during treatment, after treatment, and at 3-, 6- and 12-month following treatment cessation.

Inclusion Criteria:

• Fulfilled the Diagnostic and Statistical Manual of Mental Disorders criteria for Alcohol Use Disorder or Substance Use Disorder
• Fulfilled the Swedish criteria for homelessness and had access to "steady housing" (defined as situation 3 or 4 according to Sun et al. [2012])
• Were between 16-65 years old
• Were able to read and write Swedish and were able to carry out treatment, 5-15 sessions together with homework assignments
• Had regular contact with a social worker at the social welfare office for the homeless.

Exclusion Criteria:

• Another primary psychiatric condition (e.g., bipolar disorder, psychosis, suicidal ideation)
• Failure to attend first two treatment sessions
• Other aggravating circumstances, for example violence in close relationships.

Data is not possible to share du to integrity reasons, as the study participants were patients.