Activation syndrome consists of 10 suicides associated symptoms, which is induced by antidepressant treatment. These are anxiety, agitation, manic episodes, sleep disruption, irritability, hostility, aggressiveness, impulsivity, akathisia and mania/hypomania. This syndrome is reported to be associated with a bipolar disorder diathesis. The aim of this study is to evaluate lifetime hypomanic symptoms with major depressive disorder, who are prescribed antidepressant medication, and to investigate whether there is a relationship between these symptoms and the development of AS.

Sixty consecutive outpatients with the diagnosis of major depressive disorder who were naturalistically given antidepressant treatment were examined prospectively. Patients were assessed three times; at baseline, 2 and 4 weeks later. At baseline visit, clinical characteristics of patients including Ghaemi criteria were assessed, life-time history of hypomanic symptoms were assessed with the Hypomania-Checklist-32. In all three interviews, Barnes Akathisia Rating Scale, Hamilton Rating Scale for Depression, Hamilton Anxiety Rating Scale and Young Mania Rating Scale were applied to detect the symptoms of AS. The patients who present at least one of the 10 symptoms were considered to have AS.

Of the 60 patients 25(41.7%) developed AS. The most prevalent symptoms of AS are insomnia (31.7%), anxiety (25%) and irritability (15%). Significant difference was found between patients with and without AS, with regard to HCL-32 test scores. A moderate correlation between the number of AS symptoms and HCL-32 test scores were determined. AS was found to be significantly more frequent in patients with mere hypersomnia and both increased appetite and hypersomnia those without these symptoms.

The findings of this study suggest that certain features of BPS might be associated with the development of AS. Antidepressant treatment of depressive illnesses in this spectrum which are misdiagnosed as unipolar may reveal these symptoms that will complicate the current episode and destabilize the longitudinal course. For this reason, clinicians should evaluate the patients who present antidepressant induced symptoms meticulously and be careful not to overlook the characteristics of BPS.