A longitudinal study of a representative sample of 1970 college students disclosed that a great majority of students who had used marihuana reported "no effect" or "improved" adjustment in 1972, but a small group reported worsened adjustment and showed a clear trend to have decreased or quit the use of the drug. Many others who quit or reduced their use of marihuana, nevertheless reported its effects as favorable. No significant difference in grade point average or educational achievement was found between users and nonusers.
Marihuana users experienced somewhat more difficulty in deciding on career goals and left college a little more often (than nonusers) to reassess their goals. Amotivational syndromes, if they occurred, were not observed in a large number of students who, despite using marihuana, were continuing to function satisfactorily.
Brill NQ, Christie RL. Marihuana Use and Psychosocial AdaptationFollow-up Study of a Collegiate Population. Arch Gen Psychiatry. 1974;31(5):713-719. doi:10.1001/archpsyc.1974.01760170099016