Does subclinical hyperthyroidism predispose to cocaine addiction?

To investigate the relationship between subclinical hyperthyroidism and cocaine abuse.

Using the computerized patient medical record system at the Veterans Affairs Medical Center in Memphis, Tennessee, we identified the following 3 groups: (1) cocaine abusers without hyperthyroidism; (2) patients with hyperthyroidism without cocaine abuse; and (3) patients with hyperthyroidism and cocaine abuse. In 1,191 patients taken from the same clinic population, we calculated the prevalence of cocaine abuse alone, hyperthyroidism alone, and both diagnoses together to examine whether a relationship existed between hyperthyroidism and cocaine abuse.

We found the following prevalences: (1) 37.7 per 1,000 patients with cocaine abuse; (2) 18.8 per 1,000 with hyperthyroidism (primarily subclinical); and (3) 65.4 per 1,000 with both hyperthyroidism and cocaine abuse. We found a highly statistically significant correlation between subclinical hyperthyroidism and cocaine abuse (P<<.01 by χ² test) in this population of Veterans Affairs patients. No other significant correlations were found.

In our study population, we found a strong correlation between hyperthyroidism (overt or subclinical) and cocaine abuse. Several theoretical mechanisms may explain these findings, but further prospective studies are needed to clarify this complex relationship.