Study links leptin levels with symptoms of depression, anxiety

Oct 21 2011

A new study has for the first time in humans linked levels of leptin, a hormone produced by fat cells, with symptoms of depression and anxiety independent of weight. The study, published in the journal Clinical Endocrinology and led by Dr Elizabeth Lawson from Harvard Medical School and Massachusetts General Hospital, USA, suggests that leptin levels may be related to depressive and anxiety symptoms in women regardless of weight or body fat.

Lawson and her team studied 64 women in four groups: 15 with anorexia nervosa, 20 normal weight and healthy, 17 overweight or obese, and 12 normal weight with hypothalamic amenorrhoea (women with this condition do not menstruate and have low leptin levels, but unlike anorexic women their fat levels do not differ from healthy controls). They measured fasting blood leptin levels, weight, and total body fat, and administered tests for depression and anxiety symptoms, and levels of experienced stress (HAM-D, HAM-A and Perceived Stress Scale respectively; higher scores signify increased symptoms).

Women with lower symptoms of depression and anxiety exhibited higher leptin levels and vice-versa. HAM-D and HAM-A scores across the groups were negatively correlated with leptin levels (HAM-D: r = -0.43, P = 0.0004; HAM-A: r = -0.34, P = 0.006). This remained significant after controlling for both fat mass and body weight. Perceived Stress Scale scores were also negatively correlated with leptin levels (r = -0.35, P = 0.007), although this did not remain significant after controlling for fat mass or body weight. Women in all groups who scored above eight (a standard cutoff signifying depression) on the HAM-D score exhibited lower leptin levels than those scoring below the cutoff. This also remained significant after controlling for fat mass and body weight.

These findings show for the first time in humans that levels of the hormone leptin (known to be one of the group of hormones involved in appetite regulation) and symptoms of depression and anxiety are negatively correlated, independently of fat mass or body weight. This independence strengthens the link because it controls for confounding relationships between fat mass and leptin. Further studies with larger sample sizes are now needed to determine exactly how leptin and depressive and anxiety symptoms interact.

Lead researcher Dr Elizabeth Lawson from Massachusetts General Hospital and Harvard Medical School, USA said:

"To find that leptin levels and symptoms of depression and anxiety are linked in humans, independent of body fat, is very interesting, as animal studies suggest that leptin has anti-depressant and anti-anxiety properties.

"Our findings place leptin on a growing list of hormones that are correlated with psychiatric symptoms. Whether leptin influences depression or vice versa, and whether the relationship is direct or mediated by a third as yet unknown factor needs to be investigated.

"Further studies administering leptin to patients will be important in determining whether this hormone has a potential role in the treatment of depression and/or anxiety."