L-lysine treatment could improve symptom severity and cognitive deficits in patients with schizophrenia, according to a study conducted by a team of Swedish researchers.

The study investigated the benefit of L-lysine, an amino acid that occurs naturally in food and interferes with nitric oxide production, as a treatment for schizophrenia.

Ten patients with schizophrenia were administered with 6g/day doses of L-lysine in addition to conventional antipsychotic treatment as part of the single-blinded, cross-over study.

Patients were randomly assigned to treatment with either L-lysine or placebo and screened at baseline after four weeks, when treatment was crossed over, and after eight weeks, when treatment was been terminated.

The four-week treatment caused an increase in blood concentration of the amino acid and was tolerated well, while two patients showed no increase in blood levels.

The remaining eight patients showed a decrease in symptom severity as measured by Positive and Negative Syndrome Scale.

The patients’ ability to solve the Wisconsin Card Sorting Task also improved, indicating increased problem solving capacity and cognitive flexibility.