[6]
... The behavioral and biological concomitant of chronic marijuana use were studied in a group
of heavy and casual users under controlled research ward conditions.
Assessments of operant work performance revealed that most subjects showed no
impairment in motivation to work for money reinforcement even when they smoked
a large number of marijuana cigarettes. Some dose related decrement in
performance was noted following days of heavy marijuana smoking. However, these
decrements were probably not biologically significant. No changes were observed
in a large series of physical and laboratory assessments following marijuana
smoking.
The only significant changes were those related to vital capacity (lung
function) and these changes may be more closely related to the processes of
smoking per se than to the pharmacological actions of marijuana.
No changes in testosterone level were observed following chronic
marijuana smoking. Significant weight gain was associated with marijuana
smoking. Marijuana also appeared to influence a number of complex social and
psychological factors associated with personal interaction. No evidence was
obtained that marijuana produces any significant adverse effects on cognitive
or neurological function.