A Double Blind Placebo Controlled Study of Valacyclovir in Cognitive Impairment and Mood Symptoms of Bipolar Disorder

Background

Herpes Viral Infections and Mental Illness. Recent studies have suggested that chronic, recurrent infections with the herpes family of viruses may play a role in chronic mental illnesses such as schizophrenia and bipolar disorder. Several studies have indicated that individuals with schizophrenia have evidence of increased exposure to Herpes virusesthough this has not been found in all studies . Leweke et al found that untreated individuals with recent first episode schizophrenia had increased levels of serum and cerebrospinal fluid (CSF) immunogloublin G (IgG) antibodies to Cytomegalovirus (CMV) and Toxoplasma gondii in comparison to controls without psychiatric illness. Notably, serum immunoglobulin M (IgM) levels were not increased indicating that infection had not occurred recently. Treated individuals with schizophrenia had similar antibody levels as controls. Finally, Dickerson et al have recently shown that previous Herpes Simplex Virus -1 (HSV-1) infection is associated with cognitive impairment in bipolar disorder, with a relative risk of 22.2 and that this risk was increased in the presence of the catechol-o-methyltransferase (COMT) 158 Val/Val genotype.

It is well known that active replication of herpes viruses may occur after extended periods of latency. It has also been shown active replication of the virus in the central nervous system may be triggered by environmental or psychosocial stressors and cause mood and even psychotic symptoms. Taken together with the evidence of increased exposure to Herpes viruses found in individuals with schizophrenia and bipolar disorder, one hypotheses that remains to be tested is that episodic reactivation of Herpes Simplex 1 (HSV-1) in the brain triggered by environmental stressors could be a pathogenic mechanism contributing to symptomatology in a subset of bipolar disorder and schizophrenic patients.

Cognitive Impairment in Bipolar Disorder

Cognitive, or neuropsychological, functioning is one of the major domains of symptomatology in major mental illness. While cognitive impairment in schizophrenia has been long established, neuropsychological functioning in bipolar disorder has been less extensively studied. Nevertheless, there is evidence that patients with mood disorders frequently manifest cognitive deficits in attention, executive and memory functions. While symptomatic bipolar disorder patients have been shown to have widespread cognitive abnormalities, evidence from many studies also supports the hypothesis that there are persistent residual cognitive impairments in patients in the euthymic phase of illness. As noted above, Dickerson et al have very recently shown an association between HSV-1 seropositivity and cognitive dysfunction in bipolar disorder (2006).