This study will evaluate the potential therapeutic value of two neurosteroid treatments (DHEA and pregnenolone) in the treatment of tobacco withdrawal symptoms. This will include assessing whether these agents relieve craving for cigarettes elicited by exposure to a mildly stressful cognitive task. Pregnenolone (400 mg orally), DHEA (400 mg orally) and placebo will be administered one at each of the three sessions in a randomized order.