Bill, The following are excerpts from a UC Davis study.
http://neuro.psychiatryonline.org/cg...l/15/3/317#ABS
"In methamphetamine-naïve humans, low doses produce a sense of heightened alertness, attentiveness, and energy. Higher dose intoxication produces a sense of well-being, euphoria, and enhanced self-esteem that can approach hypomania and grandiosity. Initially, sexual activity and pleasure may be increased, although longer use is associated with impaired sexual functioning. Appetite is suppressed. Adverse effects include restlessness, insomnia, bruxism, and excessive weight loss. Suspiciousness may occur and can develop into a full paranoid psychosis that is indistinguishable from acute paranoid schizophrenia. The psychosis may extend beyond the period of acute intoxication, and some experts believe that it may recur or become chronic, despite abstinence from drug use.10–12 A preoccupation with minutiae and details can arise, leading to compulsive repetitious behaviors. Skin picking is not uncommon and is, at times, accompanied by tactile hallucinations and delusions of parasitosis. Abrupt cessation of long-term use produces withdrawal, which can last for days and may be accompanied by dysphoria, irritability, and agitation.
"...recent studies have shown that long-term methamphetamine use is associated with impaired performance on a number of cognitive tasks.68–71 Volkow et al.71 tested a group of methamphetamine-dependent subjects and found that they exhibited performance deficits in both verbal memory and motor function. Simon et al.70 observed that the methamphetamine users in their study did not differ from controls on global Intelligence Quotient (IQ) measures, though they did perform significantly worse on tests of memory recall. The methamphetamine group in this same study had difficulty with tests that measured manipulation of information (i.e., Digit Span Task and Trail Making Part B), but had no problems on tasks that measured psychomotor speed separately (i.e., Trail Making Part A). The methamphetamine group also displayed deficits in abstract reasoning and task shifting strategies. In their study, Ornstein et al.72 reported that methamphetamine-dependent subjects displayed specific deficits in shifting categories on a computerized task shifting experiment when compared with chronic heroin users and nonsubstance using control subjects."
..."Clinically, methamphetamine-dependent individuals appear distractible and exhibit difficulties in sustaining attention."....