Little is known about long-term effects of psychotherapy on depressive or anxiety disorders.

To compare the effectiveness of three psychotherapies of different length in a clinical trial with a 5-year follow-up.

In the Helsinki Psychotherapy Study, 326 outpatients with mood or anxiety disorder were randomly assigned to longterm psychodynamic psychotherapy (LPP), short-term psychodynamic psychotherapy (SPP), and solution-focused therapy (SFT), and were followed up for 5 years from start of treatment. Depressive, anxiety and general psychiatric symptoms (BDI, SCL-90-Anx, and SCL-90-GSI), working ability (WAI), and recovery (based on changes in psychiatric symptoms and use of auxiliary treatment) were used as outcome measures.

For patients with depressive disorder LPP was more effective than SPP or SFT in reducing symptoms, improving work ability and leading to recovery during the 3 last years of follow-up. For patients with anxiety disorder effectiveness of LPP was less pronounced with no differences between short-term and long-term therapy in recovery from anxiety symptoms. No differences were found between the effectiveness of the short-term therapies.

Long-term psychotherapy is more effective than short-term therapy during a long follow-up especially in the treatment of depressive disorder. More research especially considering different anxiety disorders is still needed.