For the first time an investigation has been able to link human levels of leptin, a hormone produced by fat cells, with symptoms of anxiety and depression independent of weight . The study, led by Dr Elizabeth Lawson from Harvard Medical School and Massachusetts General Hospital, USA, indicates that, regardless of body fat or weight, leptin levels might be associated with anxiety and depressive symptoms in women. The investigation is published in the journal Clinical Endocrinology.
Together with her team, Lawson examined 64 women in four groups:
20 women who were of normal weight and healthy.
15 women with anorexia nervosa.
17 women who were overweight or obese.
and 12 women who were normal weight but had hypothalamic amenorrhoea (a condition which stops menstruation for several months. Women with this condition have low leptin levels, but unlike those who are anorexic their fat levels do not differ from healthy women.)
The researchers measured fasting blood leptin levels, total body fat, and weight. They then conducted tests for anxiety and depression symptoms as well as levels of experienced stress (HAM-D, HAM-A and Perceived Stress Scale respectively; higher scores indicate increased symptoms.)
They discovered that women who experienced lower symptoms of anxiety and depression showed higher leptin levels and vice-versa. Across the four groups, HAM-D and HAM-A scores were connected with leptin levels (HAM-D: r = -0.43, P = 0.0004; HAM-A: r = -0.34, P = 0.006). Remaining considerable after controlling for both body weight and fat mass. In addition Perceived Stress Scale score were also linked with leptin levels (r = -0.35, P = 0.007), however, this didn’t remain considerable after controlling for body weight or fat mass. Across all groups, women who scored eight or above (a standard cutoff indicating depression) on the HAM-D score showed lower leptin levels compare to those who scored below 8, which after controlling for body weight and fat loss also remained considerable.
These discoveries reveal for the first time the levels of the hormone leptin (one of the hormones that controls appetite regulation) in humans, are linked to symptoms of anxiety and depression, regardless of body weight of fat. This independence makes the connection stronger as it controls for confounding relationships between leptin and fat mass. Additional investigators with more participants are needed in order to find out precisely how anxiety and depressive symptoms and leptin interact.
Lead researcher Dr Elizabeth Lawson from Massachusetts General Hospital and Harvard Medical School, USA explained:
“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.”
Written by Grace Rattue