The effectiveness of psychological treatment in psychiatric care remains a subject of ongoing debate, with varied perspectives on its impact, appropriate methods, and limitations. Substantial resources are dedicated to psychological interventions as a complement to medical treatments for psychiatrically burdened patients in outpatient care. However, empirical evidence on the outcomes of such treatments for this specific patient group remains limited. This thesis seeks to address this knowledge gap by evaluating the effectiveness of psychological treatment in psychiatry from different perspectives.

Study I examined the outcomes of psychological treatment in outpatient psychiatric settings. A total of 325 patients participated with an average treatment duration of 12.4 months. These patients represented a group with significant psychiatric difficulties and challenges, many of whom had prior psychiatric hospitalizations, previous psychological treatments, and ongoing pharmacological interventions at therapy onset. Results showed statistically and clinically significant improvements in symptoms of anxiety and depression, with symptom levels decreasing by approximately one-third across assessment instruments at treatment completion. Quality of life improved by 15% at post-treatment. Between 49–63% of patients achieved reliable or clinically significant improvements on symptom measures, while 5–12% experienced symptom deterioration, consistent with findings in similar studies. Improvements in depression and overall psychiatric symptoms were largely sustained at follow-up, though some deterioration was noted for anxiety and quality of life. The results demonstrate the substantial benefits of psychological treatment in psychiatric care and how such interventions function in clinical practice.

Study II focused on the impact of hazardous alcohol use on treatment outcomes in psychiatry. The duration of psychological treatment varied between 1–50 months. Among 324 patients, 30.2% exhibited hazardous alcohol use at treatment start. At completion of psychological treatment, this proportion decreased significantly to 18.7% and remained stable at 22.5% at one-year follow-up. Patients with hazardous alcohol use showed significant reductions in scores on the Alcohol Use Disorders Identification Test (AUDIT), from 12.3 at baseline to 7.9 at treatment completion, and 8.3 at follow-up. The results also suggest that hazardous alcohol use at treatment start does not hinder therapeutic progress on measures of anxiety, depression, or quality of life. Patients with hazardous use achieved outcomes that were at least as good as those without hazardous use, despite treatment not being explicitly focused on alcohol consumption.

Study III investigated differences between short- and long-term psychological treatments in relation to psychiatric severity, and outcomes. The median treatment time for all patients were approximately 43 weeks. For treatments lasting one year or less, the median was 26 weeks, and for treatments longer than one year, the median was 94 weeks. Patients with longer treatment durations presented with significantly more severe symptoms at baseline. Both short- and long term treatments led to significant improvements outcome scores by treatment completion. For patients in longer treatments, no actual changes were observed after the first year of therapy, indicating that the Good-Enough-Level (GEL) model best describes the outcomes for psychiatric patients, as treatment appears to continue until a sufficiently good result is achieved.

These studies have several limitations, including the lack of randomization, the absence of a control group, and no oversight of which patients were excluded. Attrition may also have influenced the results. Additionally, factors such as medication and life events may have impacted the outcomes. These limitations reduce internal validity but enhance external validity in a real-world clinical context.

In conclusion, the findings of this thesis suggest that psychological treatment in psychiatric care primarily leads to improvements in patients' symptom levels, that patients with hazardous alcohol use derive substantial benefits from psychological treatment, and that it is of great importance to tailor the duration of treatment to individual needs and conditions, as well as to the progress of the therapy.