Kynurenic acid levels reduced in suicide attempters with schizophrenia

By Mark Cowen, medwireNews Reporter

Cerebrospinal fluid (CSF) concentrations of kynurenic acid (KYNA) are significantly lower in schizophrenia-spectrum patients with a history of suicide attempts than in those without, researchers report.

The team also found that CSF KYNA concentrations were positively correlated with CSF 5-hydroxyindoleacetic acid (5-HIAA) concentrations - the major metabolite of serotonin, which has been associated with suicidal behavior among patients with major depression.

Andreas Carlborg and team from the Karolinska Insitute in Stockholm, Sweden studied CSF KYNA concentrations collected by lumbar puncture at illness onset in 59 patients (35 men) hospitalized for psychosis symptoms between 1979 and 1987.

Of the patients, 31 were diagnosed with schizophrenia, 14 with psychosis not otherwise specified, four with schizoaffective disorder, three with schizophreniform disorder, and one with delusional disorder.

During a mean follow-up period of 22.1 years, three patients died by suicide. Nine patients had a history of attempted suicide at initial admission or during follow-up.

After accounting for age, the team found that mean CSF KYNA concentrations were significantly lower in patients with a history of suicide attempts at admission or during follow-up than in those without, at 0.83 versus 1.42 nM.

There was no significant correlation between CSF KYNA concentrations and number of days hospitalized, as an indicator of disease severity, diagnostic category, and gender.

But the team report a significant and positive association between CSF KYNA and 5-HIAA levels.

"Low concentrations of CSF 5-HIAA, a sign of dysfunction of the serotonin system, have been associated with suicidal behavior in mood disorders," say Carlborg et al.

The results, published in Psychiatry Research, suggest that "the neurochemical correlates of suicidal behavior need further investigation," they conclude.

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