Predictors of nonadherence to antidepressants in depressed patients


Why is maintenance antidepressant therapy important?

  • Of patients with a depressive disorder 50% will have further episodes
  • The recurrence rate of depression is 80 to 90% after 3 episodes
  • Poor adherence to treatment of chronic conditions such as depressive disorder is a large problem
  • Nonadherence rates in recurrent depressed patients range from 39.7% to 52.7% with a mean of 46,5% over 2 years
  • Suboptimal dosing and duration of antidepressants increases the risk of relapse and recurrence.
  • Clinicians are only 50% accurate in their identification of potentially nonadherent patients.

What are the potential risk factors for nonadherence in patients with recurrent depressive disorder? This question was recently researched and published in the Journal of Clinical Psychiatry.

The researchers assessed nonadherence with the Medication Adherence Questionnaire. Nonadherence on this scale indicates that patients missed 20% or more of the doses of their antidepressant medication. They followed 91 patients with at least 2 major depressive episodes in the last 5 years and were in remission. Follow up duration was 2 years.

In a multivariate analysis with backward elimination they found a higher level of personality pathology and higher education at baseline predictive for for nonadherence during a follow up of 2 years. These two factors explained 15% of the variance in nonadherence. All other variables such as axis 1 comorbidity, number of previous episodes, severity of residual symptoms, severity and duration of last episode, and medication did not increase the risk of nonadherence. There was no independent variable predicting nonadherence.

Limitations of this study
Besides the small sample which could have limited the power of the study resulting in a lack of identifying possible factors influencing nonadherence this study did not include other confounding factors for adherence in the patient doctor relationship such as the therapeutic alliance, patients attitudes towards the illness and the medication.
Ten Doesschate MC, Bockting CL, Koeter MW, Schene AH (2009). Predictors of nonadherence to continuation and maintenance antidepressant medication in patients with remitted recurrent depression. Journal of Clinical Psychiatry DOI: 19192463