The bioflavonoid quercetin may reverse the stress-induced biochemical and behavioural changes associated with anxiety and depression according to a recent study.
Researchers investigated the effects of quercetin on behaviour in mice using a social interaction test and a forced swimming test, a procedure used to induce stress in the animals. In doing so they found that administering quercetin in certain dosages had anxiolytic (anxiety-reducing) and antidepressant effect.
Quercetin is a bioflavonoid found in a variety of fruits and vegetables with the best sources being citrus fruits, apples, onions, red wine and black tea. It is found in smaller amounts in green leafy vegetables such as spinach and kale and is also widely marketed as a standalone nutritional supplement and as part of multi-nutrient formulas. Quercetin is best known for its antioxidant and anti-allergy properties (it is thought to reduce histamine release) but research like this current study is demonstrating it also has effects on mood and behaviour.
Anxiety and depression are extremely common with current figures for prevalence in the United States showing that 40 million people (18% of the population) aged 18 and over suffer from an anxiety disorder in any given year whilst approximately 15 million (7%) suffer from major depressive disorder. The two are often comorbid - meaning they occur together - and can cause considerable suffering and disability. According to the National Institute of Mental Health (NIMH), major depressive disorder is the leading cause of disability in those aged 15-44.
It has been well established by scientists that these mental health disorders are linked to stress and the reaction of the stress response system in the body which is governed by the hypothalamic-pituitary-adrenal (HPA) axis. Those suffering from anxiety and depression generally show increased blood concentrations of the stress hormone cortisol along with corticotropin-releasing-factor (CRF), the hormone released by the hypothalamus in response to stress that ultimately leads to the release of stress hormones such as adrenaline and cortisol by the adrenal glands. People with anxiety and/or depression therefore have a heightened sensitivity to stress.
The Indian researchers behind the current study into quercetin's effects on mood disorders found not only that the bioflavonoid acted as an anxiolytic and antidepressant but a possible mechanism behind the effect - a reduction in the effects of CRF.
Elevated CRF is thought to be one of the key biochemical factors underpinning the majority of cases of anxiety, depression and other mental health disorders, so if these findings can be shown to hold true in humans then quercetin could be important as both a preventative and treatment.
We will have to wait for future research to determine if a diet high in quercetin can help to prevent the development of anxiety and depression and whether dosages found in nutritional supplements might be an effective treatment. Until then, eating a diet high in fresh fruits and vegetables is something everyone should be doing for mental health and health in general.
Source: Bhutada P Mundhada Y Bansod K Ubgade A Quazi M Umathe S Mundhada D (2010) Reversal by quercetin of corticotrophin releasing factor induced anxiety- and depression- like effect in mice Progress in Neuro-psychopharmacology and Biological Psychiatry [Epub ahead of print]