A careful testing of the motor and sensory functions of the nervous system was included in the general physical examination of each subject. Of motor functions, reflex activity and muscular response and coordination were determined; of sensory functions, perception of touch, pain and temperature stimuli; of specialized functions, taste, hearing and vision. In the eye, the corneal and light reflexes were tested and a retinal examination was made. In this neurological examination no pathological conditions were found in any of the subjects.
In the psychiatric examination attention was paid to general intelligence and knowledge in relation to the subject's background, to relevancy of talk in conversation, to orientation as to time, place and situation, to memory of past and recent events, to ability in simple arithmetic, to judgment in reaching decisions, and to the presence of abnormal mental content shown by delusions, hallucinations, obsessions, and ideas of persecution. There was no evidence of disordered cerebral functioning in any of the group.
As would be expected, differences in grades of intelligence and in orderliness in thinking and reasoning were noticeable. The Bellevue Adult Intelligence Test was administered to a total of 60 male subjects, 40 marihuana users and 20 nonusers. The average I.Q. for the user group was 96.7, range 70 to 124, and for the non-user group the average I.Q. was 104.5, range 93 to 114. Both groups may therefore be classified as of average intelligence.
When analyzed according to racial distribution the two groups were even better equated intellectually than the total results indicate. For the 28 white subjects examined (13 users and 15 non-users) the average I.Q. for the users was 106.1, range 77 to 124, and for the non-users the average I.Q. was 106.3, range 96 to 114. There were 24 Negro subjects, 19 users and 5 non-users. The average I.Q. for the users was 92.6, range 70 to 112, while for the non-users the average I.Q. was 98.8, range 93 to 101. Although the non-users averaged 6.2 points higher than the users, it must be taken into account that the number of Negro non-users tested was small. In any event, the disparity in results would not be considered significant. The average I.Q. of the 2 Puerto Rican users was 91.0, range 72 to 100.
Reports on mental deterioration due to toxic, organic or psychotic factors as given in the literature reveal that in such cases the individual scores on the Bellevue Adult Intelligence Test show marked irregularity, depending upon the functions involved in the deteriorative process. As a group, the marihuana users tested in this study showed very even functioning, and what little irregularity occurred can be explained on the basis of language and racial factors.
The physical and psychiatric examinations were of a qualitative rather than a quantitative nature. In the special examinations and tests of organ and system function, quantitative measurements were obtained for 17 marihuana users. These subjects were selected for the reason that they had smoked marihuana for the longest period of time. The figures for years of usage and number of cigarettes smoked daily were taken from each subject's statement.
Marihuana users accustomed to daily smoking for a period of from two and a half to sixteen years showed no abnormal system functioning which would differentiate them from the non-users.
There is definite evidence in this study that the marihuana users were not inferior in intelligence to the general population and that they had suffered no mental or physical deterioration as a result of their use of the drug.