New Study Shows Effects of Green Tea on Depression

The American Botanical Council has just recently released a new report claiming that increased green tea intake can enhance reward learning and decrease symptoms of depression. Reward learning is the conditioning response of positive behavior following a positive event. Positive reward learning is thought of as a way to counter depression.

thumb_logo_abc_american_botanical_council.jpgThe authors of the study began their experiments with a hypothesis that “chronic treatment with green tea would improve reward learning compared with a control treatment.” In this random, double-blind study, participants were monitored to effectively evaluate the effects of green tea on reward learning and depression symptoms.

Held at Shandong University in Shandong, China, the study, comprised of 46 voluntary participants ranging in age from 18-34, ran from March 2012 until November 2012. At the baseline of the study, all of the participants were similar in age, education, and daily behavior.

Each participant was randomly assigned to either the green tea group or the placebo group. The green tea group consumed 400 mg of green tea powder three times each day while the placebo group consumed 400 mg of cellulose powder three times each day. The green tea powder had to be consumed 30 minutes after each meal by dissolving it in hot water.

To assess the reward learning processes and depressive behaviors of the participants, the authors of the study set up tasks comprised of 30 reward trials, no 30 no-reward trials, and 30 fixation periods. The subjects could win money by pressing a button during a target presentation. If a subject pushed the target in a rewarding trial, he or she earned 1 Yuan. The subjects were told they would receive one-third of the money they won during the trials in each session at the end of the study.

The study results show that the green tea group had a significantly shorter reaction time in response to the reward trial compared with the placebo group, suggesting that those who consumed green tea exhibited significantly increased reward learning. No differences were observed in the reaction time in the no-reward trials between the 2 groups.

“It has been evidenced that reduced dopamine neurotransmission might contribute to the anhedonia (the inability to experience pleasure) and loss of behavioral incentive in depressive disorder, therefore it is important to examine the regulatory role of green tea on the brain circuitry activated by reward learning,” write the authors.

The findings in this study suggest that drinking green tea for 5 weeks was beneficial for reward learning and the improvement of depressive symptoms.

“We propose that green tea would probably have the potential for normalization of anhedonia through improve[d] reward learning and have implications for the prevention of depression,” conclude the authors.

Read the full study here.

SOURCE: The American Botanical Council