Changes in serotonin function and disturbances in tryptophan availabil
ity have been implicated in many psychiatric disorders, including alco
holism. In the present study we took serum free tryptophan samples fro
m 31 healthy volunteer controls and from 42 DSM-III-R alcohol-dependen
t subjects who had abstained from alcohol for at least 2.5 weeks (rang
e 2.5-104 weeks). We also measured the basal serum cortisol level at 0
9.00 hours for the same subjects and controls. There was a significant
increase in the serum tryptophan level of the alcoholic subjects, by
43.7 mu mol l(-1) (range 29-63 mu mol l(-1)), regardless of age of ons
et of alcoholism, family history of alcoholism or sociopathic traits,
compared to the controls (33.0 mu mol l(-1), range 19-60 mu mol l(-1))
. There was also an increase in the basal serum cortisol level in the
alcoholic subjects compared to the controls, but this was not related
to the increase in tryptophan levels. These findings indicate a distur
bance in serotonin precursor availability in post-withdrawal alcoholic
s, and contribute to the evidence for involvement of the serotonin sys
tem in alcoholism.