Mirtazapine for Generalised Anxiety Disorder

This is an open label study of 44 adult outpatients with generalised anxiety disorder treated with a fixed-dose of Mirtazapine. The authors begin by introducing Mirtazapine as a NaSSA (Noradrenergic and specific serotonergic antidepressants) which inhibits autoreceptors and 5-HT2/5-HT3 receptors. In the study, people were recruited from the psychiatric liaison service. Exclusion criteria included comorbid mental illness and previous ECT or other psychotropic medication within the previous 6 months. A Hamilton-Anxiety score of at least 20 was required for entry. 44 people were enrolled. If people dropped out, then their last results were carried forwards for the purposes of analysis.

They found a mean reduction from baseline of 63% on the HAM-A Total and similar scores for the psychic and somatic subscales. Response was defined as a greater than 50% increase in the HAM-A Total and 1 or 2 on the Clinical Global Impression Scale. 35 people were responders and 9 were non-responders which initially sounds quite good as the mean duration of illness was just over 12 years! There were symptom improvements as early as the first week. The most common side-effects were appetite and weight gain (25%) as well as drowsiness (20.5%).

One of the difficulties with this study is of course the lack of a placebo group. The authors mention this in the discussion. On one level however, this is exactly what we see in practice. When the psychiatrist prescribes a medication, the patient’s response will result from the biological properties of the medication and the so-called ‘placebo-response’. In this sense, we could predict from this study that if we measured people’s responses in a clinical scenario with HAM-A scales then over 12-weeks roughly 80% of people should be responders. It’s a little more tricky to extrapolate some of the other figures as no confidence interval is included for the HAM-A reduction. We might ask, ‘does it matter that it’s a placebo response?’. The real issue is what harm can the medication do and can we appropriately judge the risk-benefit ratio. In the same way that the placebo effect applies to the benefits of a medication, so too does it apply to the side-effects. Thus the weight gain and drowsiness may be partly attributable to this effect although they are well documented side-effects of Mirtazapine. Lastly, the study was only 12-weeks long, a relatively small proportion of the 12 years of illness duration and so as well as a placebo controlled trial, a prospective study would also be of benefit.

The study is a preliminary one, examining the question of using Mirtazapine in Generalised Anxiety Disorder and providing some useful results in the process.

STT 1

References

Gambi, F et al. 2005. Mirtazapine treatment of Generalised Anxiety Disorder: a fixed dose, open label study. Journal of Psychopharmacology. 19(5). 483-487.

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