Exploratory investigation of biomarker candidates for suicide in schizophrenia and bipolar disorder

Clozapine and lithium increase neurosteroids in rodents, and both drugs demonstrate antisuicidal actions. We therefore hypothesized that neurosteroid levels may be reduced in patients with schizophrenia or bipolar disorder who completed suicide.

To investigate neurosteroid levels in the parietal cortex and posterior cingulate in schizophrenia and bipolar patients who died by suicide, and compare them with patients with these disorders who died of other causes.

Neurosteroid levels were quantified by gas chromatography/mass spectrometry in the parietal cortex and posterior cingulate. Mann-Whitney analyses were conducted in exploratory post hoc analyses to investigate neurosteroids as possible biomarker candidates for suicide.

The study showed that pregnenolone was significantly decreased in the parietal cortex in the combined group of patients with schizophrenia or bipolar disorder who died by suicide (n = 13) compared with patients with these disorders who died of other causes (n = 17, p = .02). Pregnenolone levels were also lower in the parietal cortex in the individual group of schizophrenia patients who died by suicide (n = 4) compared with schizophrenia patients who died of other causes (n = 11) p = .04).

Pregnenolone alterations may be relevant to the neurobiology of suicide in schizophrenia and bipolar disorder.