Because hormones are critically important for overall health and performance, it is important to understand how marijuana affects these systems. Numerous forums insist that marijuana induces unfavorable hormonal changes. For instance, marijuana has been shown to suppress the hypothalamic-pituitary axis (HPA) in rodents , but human studies suggest variable effects on the HPA axis . In both males and females, a realistic dose of THC (cigarettes containing % THC) immediately lowered Luteinizing Hormone (LH) and raised the dangerous stress-associated hormone cortisol , which may underly the paranoia some users experience. A recent study , one of the few with sufficient sample sizes, showed that the cortisol response to physiologically-relevant amounts of THC was blunted in chronic cannabis users; while plasma cortisol levels increased in a dose-dependent manner in both non-users and frequent users, frequent users showed less of a cortisol surge.