The study will be published in the American Journal of Chinese Medicine.

Depression is a common psychiatric disorder with a high morbidity and mortality rate. The pharmacotherapy used in clinic today is not suitable for all patients and causes certain side-effects. Thus, looking for alternative treatments with antidepressant effect and minimal side-effect is important.

Gastrodia elata Bl. (tin ma,) is a famous Chinese traditional medicine used for centuries.

What is Tin Ma? The earliest account of tin ma was recorded in Shennong Bencao Jing ("The Herbal Encyclopedia of Shennong"), which is considered the oldest Chinese medicine text in history. The name(s) of author(s) have been lost through time but the book is believed to be at least 2200 years old.

The encyclopedia lists tin ma as being able to "treat aching of the brain"and to "calm one's emotion" and to help people sleep. In modern times, tin ma has been used to treat hypertension, dizziness, headache, and somatic paralysis to name a few. Tin ma is also considered to be anti-epileptic, anti-arthritic with the abilities of calming emotions (and thus depression) and soothing pain.

It is mainly produced in Sichuan, Yunnan and Guizhou provinces. Other producing regions include Northeast China and North China. Nowadays, wild tin ma is rare and its prices are dear. Tin ma farms are abundant in China.

The present study tested the anti-depressant effect of tin ma extract on rats that went through the forced-swimming test. Rats were fed with tin ma extract or fluoxetine (Prozac).

What is forced-swimming test? It's a behavioural despair test used to measure the effect of antidepressant drugs on the behaviour of laboratory animals (typically rats or mice).

Animals are subjected to two trials during which they are forced to swim in an acrylic glass cylinder filled with water, and from which they cannot escape. The first trial lasts 15 minutes. Then, after 24-hours, a second trial is performed that lasts 5 minutes. The time that the test animal spends without moving in the second trial is measured. This immobility time is decreased by antidepressants.

The results indicated that the duration of immobility was significantly decreased in rats fed with tin ma extract. However, the concentration of serotonin, the "happy hormone", and 5-hydroxyindoleacetic acid and their ratio in frontal cortex, amygdala, and hippocampus were not significantly different between the tin ma and the control groups.

Nonetheless, tin ma significantly increased dopamine levels but decreased the concentration of 3,4-dihydroxyphenylacetic acid (which metabolizes L-DOPA, a precursor of dopamine) and decreased dopamine turnover in striatum in the brain compared to the control.