Adherence to drug treatment is a constant challenge for mental health practitioners, so any research that explores why patients stop taking their medication is usually of interest.

There are many published studies that look at the reasons why people decide to stop taking their antidepressants, and these range from finding it difficult to cope with the side effects to just not wanting to be popping pills on a regular basis.

This randomised controlled trial conducted by researchers from Little Rock, Arkansas, examines the experiences of veterans (mostly middle-aged and elderly men) prescribed antidepressants, specifically with regard to different types of non-adherence, reasons for non-adherence, and side effects.

The trial involve 395 patients with depression and adherence was measured from patient self-report and pharmacy data. Patients were categorised as adherent if they reported taking the full dosage ≥80% of the time. Adherence was also measured using medication possession ratios calculated from administrative pharmacy data.

Here’s what they found:

• 72.1% of patients prescribed antidepressants reported adherence at 6 months, 70.8% reported adherence at 12 months. However, only 48.5% and 46.1% had medication possession ratios ≥0.8 during these periods
• Of patients with self-reported adherence, only 19.4% responded to treatment by 6 months and 28.5% responded by 12 months
• 25.2% of patients with medication possession ratios ≥0.8 responded to treatment by 6 months and 27.7% responded by 12 months
• Of the 27.9% who reported being non-adherent at 6 months:
• 4.8% had never taken the antidepressant,
• 12.2% stopped taking the antidepressant and
• 10.9% were not taking the antidepressant as prescribed (i.e. taking the full dose <80% of the time)
• Of the 29.2% who reported being non-adherent at 12 months:
• 8.6% had never taken the antidepressant
• 14.4% stopped taking the antidepressant and
• 6.2% were not taking the antidepressant as prescribed
• Concern about side effects was the most common reason (72.7% at 6 months and 47.6% at 12 months) and the most commonly cited most important reason (40% and 23.5%) given for never taking the prescribed antidepressant
• At 12 months, not thinking they needed antidepressants was equally commonly cited as the most important reason for never taking antidepressants (23.5%)
• Feeling that the drugs would not work was the most common (46.4%) and most commonly cited most important reason (28.6%) given for stopping the prescribed antidepressant at 6 months
• At 12 months, the most common reason for stopping was the belief that they should be able to solve their problems without antidepressants (54.3%) and the most commonly cited most important reason was having side effects (22.9%)
• Of patients still taking antidepressants at the 6-month follow-up, 81.9% reported at least one side effect and 43.6% reported at least one severe side effect. At 12 months, 81.8% reported at least one side effect and 40.6% reported at least one severe side effect.

The authors concluded:

In this sample of mostly middle-aged and elderly men with depression, treatment non-response and side effects were the rule rather than the exception. These findings suggest that non-adherence may have resulted primarily from patients’ negative experiences with antidepressants rather than structural barriers or non-compliant behaviours.

Fortney JC, Pyne JM, Edlund MJ, Stecker T, Mittal D, Robinson DE, Henderson KL. Reasons for antidepressant nonadherence among veterans treated in primary care clinics. J Clin Psychiatry. 2011 Jun;72(6):827-34. Epub 2010 Nov 16. [PubMed abstract]