by Fleur Borrelli, nutritionist at The Putney Clinic of Physical Therapy The skin and the brain are intricately linked. Both produce the same hormones and neurotransmitter substances. In the skin, serotonin should be converted to melatonin which acts as a natural antibiotic and anti-inflammatory. It is no wonder, therefore, that the skin condition psoriasis is linked to both depression and anxiety disorders (1) . A lack of nutritional cofactors such as vitamins B6 and B12 may prevent this conversion in a biochemical process known as methylation. Geographical latitude may also influence incidence of psoriasis as beneficial sunlight is also needed to produce melatonin (2) . Overuse of sunscreens and lack of exposure to the sun will also inhibit the production of vitamin D, vitally important for the integrity of the barriers of the body which include the intestinal lining, the blood brain barrier, the synovial lining and of course the skin (3) . The function of the barriers is...