New analysis reveals insights into long-term effects of antidepressant drugs

In the current issue of Psychotherapy and Psychosomatics a new analysis discloses insights into the long term effects of antidepressant drugs. Major depressive disorder (MDD) is more often chronic or recurrent in clinical than in community samples. For example, perhaps 85% of patients but only 35% of persons in the community with MDD experience another depressive episode within 15 years. Nonetheless, active treatments including antidepressant medication or cognitive therapy reduce depressive symptoms and delay relapse compared to inactive controls. Follow-ups of treated and untreated persons in clinical trials have rarely exceeded 1-2 years, however.

The current analyses of a national sample with 9-year follow-ups clarified these possibilities. Using the same assessments for treated and untreated persons excluded the first possibility. Testing whether MDD severity and a wide range of demographic, psychosocial, and clinical variables accounted for long-term differences between treated and untreated persons estimated the second possibility, with remaining outcome differences more likely due to treatment. Twelve-month MDD prevalence at survey waves 1, 2, and 3 was 13.3, 10.5, and 9.9%, respectively. With MDD, 38.1% of participants received no treatment, 25.2% inadequate treatment including medication, 19.2% inadequate treatment without medication, 13.5% adequate treatment including medication, and 4.1% adequate treatment without medication during the past year.

Prior depressive status, treatment and their interaction, predicted subsequent depressive symptom levels. Among persons with major depressive disorder, symptoms were higher after inadequate treatment, adequate treatment, treatment without medication, or treatment including medication compared to no treatment, and symptoms were higher after treatment including medication versus treatment without medication. In addition, among persons with major depressive disorder, symptoms were higher after inadequate treatment, adequate treatment, or treatment including medication compared to no treatment, and symptoms were higher after treatment including medication versus treatment without medication.

These findings show that symptoms were more sharply elevated 9 years following treatment including medication than treatment without medication, and major depressive disorder severity plus other covariates did not account for increased depression after medication. Patient characteristics accounted for symptoms after treatment without medication, however. This pattern suggests possible long-term iatrogenic effects of antidepressants.