Cerebrospinal fluid biochemical examinations: do they reflect clinical or biological differences?

5-Hydroxyindoleacetic acid (5HIAA), homovanillic acid (HVA), cortisol (CS), tryptophan (TRY), and calcium (Ca) concentrations were measured in the spinal fluid of 85 female psychiatric inpatients in a drug-free state; 32 women suffered from major depression, another 32 had schizophrenic (or schizophreniform) disorder, and 21 had alcohol dependence as defined by DSM-III criteria. A dexamethasone suppression test (DST) was carried out following lumbar punctures in all patients. Biochemical results were analyzed by two-way analysis of variance to test the effect of diagnosis and dexamethasone nonsuppression. CS concentration proved to be significantly higher in dexamethasone nonsuppressors, independent of the diagnosis. HVA was lower in nonsuppressors, particularly in alcohol-dependent patients; 5HIAA showed a tendency to be higher in nonsuppressor depressed patients. TRY was again higher in nonsuppressors, significant only in schizophrenic patients. Ca concentration was higher in depression and lower in alcohol dependence, and within the depression group it was higher in normal DST patients. The results indicate that the primarily biological dysfunction, i.e., the limbic-hypothalamic disinhibition reflected in the DST, may be more closely related to spinal fluid biochemistry than clinical syndromes.