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BACKGROUND Although cannabis is the most widely used illicit drug in the United States, its long-term cognitive effects remain inadequately studied. METHODS We recruited individuals aged 30 to 55 years in 3 groups: (1) 63 current heavy users who had smoked cannabis at least 5000 times in their lives and who were smoking daily at study entry; (2) 45 former(More)
Three experienced marijuana smokers participated in four 2-day experimental sessions in which they smoked either 0, 1, or 2 marijuana cigarettes containing 2.57% delta 9-tetrahydrocannabinol (THC) at two different times on the first day. A battery of physiological, subjective, and performance measures was repeated throughout day 1 to assess acute effects(More)
BACKGROUND Individuals who initiate cannabis use at an early age, when the brain is still developing, might be more vulnerable to lasting neuropsychological deficits than individuals who begin use later in life. METHODS We analyzed neuropsychological test results from 122 long-term heavy cannabis users and 87 comparison subjects with minimal cannabis(More)
BACKGROUND SR141716, a recently developed CB1 cannabinoid receptor antagonist, blocks acute effects of Delta-9-tetrahydrocannabinol (THC) and other CB1 cannabinoid agonists in vitro and in animals. These findings suggest that CB1 receptors mediate many of the effects of marijuana, but this has not been evaluated in humans. METHODS Sixty-three healthy men(More)
Nicotine-induced attentional enhancement is of potential therapeutic value. To investigate the precise attentional function(s) affected and their neuronal mechanisms, the current functional magnetic resonance imaging (fMRI) study used an attention task in which subjects responded to stimuli of high (INT(high)) or low intensity presented randomly in one of(More)
BACKGROUND Dopaminergic activity plays a role in mediating the rewarding aspects of abused drugs, including nicotine. Nicotine modulates the reinforcing properties of other motivational stimuli, yet the mechanisms of this interaction are poorly understood. This study aimed to ascertain the impact of nicotine exposure on neuronal activity associated with(More)
The present study compared the disposition and metabolism of the recreational drug (+/-) 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") in squirrel monkeys and humans because the squirrel monkey has been extensively studied for MDMA neurotoxicity. A newly developed liquid chromatography-mass spectrometric procedure for simultaneous measurement of MDMA,(More)
Attention-enhancing effects of nicotine appear to depend on the nature of the attentional function. Underlying neuroanatomical mechanisms, too, may vary depending on the function modulated. This functional magnetic resonance imaging study recorded blood oxygen level-dependent (BOLD) activity in minimally deprived smokers during tasks of simple stimulus(More)
Chronic cannabis (marijuana, hashish) smoking can result in dependence. Rodent studies show reversible downregulation of brain cannabinoid CB(1) (cannabinoid receptor type 1) receptors after chronic exposure to cannabis. However, whether downregulation occurs in humans who chronically smoke cannabis is unknown. Here we show, using positron emission(More)
BACKGROUND Methamphetamine (MA) use among pregnant women is a world-wide problem, but little is known of its impact on exposed infants. DESIGN The prospective, controlled longitudinal Infant Development, Environment and Lifestyle (IDEAL) study of prenatal MA exposure from birth to 36 months was conducted in the US and NZ. The US cohort has 183 exposed and(More)