Schizophrenia is a serious mental disorder that currently affects about one in every 200 people. Most patients find some relief from their symptoms by treatment with antipsychotics, however they may still suffer from cognitive and negative symptoms. These include poor concentration and memory, apathy, or a reduced ability to cope in social situations. Preliminary research published in BioMed Central's open access journal BMC Medicine shows that patients who received L-lysine alongside their normal medication found some reduction in the severity of their symptoms.

In a cross-over study, ten patients with schizophrenia were given either 6g of L-Lysine or a placebo every day for four weeks. Each of the patients had been on a stable dose of medication for the past three months and had been free from psychotic episodes for the two months before the study began. They were tested for blood levels of lysine as well as the severity of their symptoms (PANSS) and functional ability (including the Wisconsin Card Sorting and Trail Making tests) at the start, after four, and after eight weeks.

Eight of the patients responded to L-lysine treatment, as shown by an increase in blood lysine levels. For these eight there was a general trend, over most of the symptomatic and cognitive tests, for improvement due to treatment with lysine. Three of the patients reported that they themselves felt some improvement. However there was a tendency for any intervention, L-lysine or placebo, to improve PANSS scores, and familiarity with the tests improved scores for the memory and mental functioning tests. So improvement was seen using both L-lysine and placebo. Results were probably also confounded by the beneficial effect of L-lysine continuing even after treatment stopped and consequently affecting scores of patients who received placebo after lysine.

Dr Wass said, "This study is a starting place for further research into the beneficial effects of L-lysine as part of the treatment of patients with schizophrenia. It was an extremely low dose, and a small sized trial, which limited the conclusions we could draw. Nevertheless this study suggests that L-lysine may be of benefit to patients in alleviating some of the negative and cognitive effects of schizophrenia."