Effect of mirtazapine treatment on body composition and metabolism

Weight gain is a common side effect of psychotropic medications. Mirtazapine, a widely used antidepressant, induces adverse metabolic effects such as an increase in body weight. The aim of this study was to investigate the influence of mirtazapine treatment on body weight, body fat mass, glucose metabolism, lipoprotein profile, and leptin and its soluble receptor in a prospective, controlled study design.

Seven women who met the ICD-10 diagnostic criteria for a depressive episode (ICD-10: F31-F33) were assigned to monotherapy with mirtazapine and observed for a 6-week period. Seven mentally and physically healthy female volunteers matched for age and body weight served as a control group. Data were collected from November 2002 to December 2003.

The mean +/- SD body weight increased from 63.6 +/- 13.1 kg to 66.6 +/- 11.9 kg during mirtazapine treatment (p = .027). Fat mass increased in study subjects from 20.9 +/- 9.6 kg to 22.1 +/- 9.3 kg (p = .018). Insulin, glucose, and the homeostasis model assessment (HOMA) index for insulin resistance and lipid parameters remained stable. Leptin concentrations increased from 23.0 +/- 17.1 ng/mL to 40.9 +/- 27.2 ng/mL (p = .018), whereas the soluble leptin receptor concentrations remained stable during mirtazapine treatment. In the control subjects, the investigated parameters remained stable. Between-group analyses of change scores revealed significant differences for body weight (p = .010), body mass index (p = .013), fat mass (p = .035), and leptin (p = .013).

The antidepressant therapy with mirtazapine was associated with a significant increase in body weight, body fat mass, and leptin concentration. In contrast to other psychotropic medications inducing weight gain, such as some second-generation antipsychotics, mirtazapine treatment did not influence the glucose homeostasis.