[Homocysteine and neuropsychiatric disorders]

The author presents an overview of the current literature on homocysteine as a risk factor for neuropsychiatric disorders. The databases MEDLINE, Current Contents and EMBASE were searched (between 1966 and 2002) for English language publications with the key words 'Homocysteine' and 'Stroke'; 'Alzheimer Disease'; 'Cognitive Impairment'; 'Epilepsy'; 'Depression'; or 'Parkinson's disease'. Individual articles were hand searched for relevant cross-references. It is biologically plausible that high homocysteine levels may cause brain injury and neuropsychiatric disorders. Homocysteine is proatherogenic and prothrombotic, thereby increasing the risk of cerebrovascular disease, and may have a direct neurotoxic effect. Evidence for homocysteine as a risk factor for cerebral microvascular disease is conflicting but warrants further study. Cross-sectional and some longitudinal studies support increased prevalence of stroke and vascular dementia in hyperhomocysteinemic individuals. The evidence of increased neurodegeneration is accumulating. The relationship with depression is still tentative, as it is with epilepsy. Currently, treatment studies are necessary to place the evidence on a stronger footing, and maybe high-risk patients should be screened for hyperhomocysteinemia and this should be treated with folic acid. More research evidence is necessary before population screening can be recommended.