Extrapolating from the follow-up questionnaires, we estimate that if all had been returned the total number of adverse reactions would be approximately 4,100. The discrepancy between the 8,958 cases reported by the respondents to the initial questionnaire and the extrapolated figure of 4,100 cases derived from the responses to the second questionnaire is worth consideration. Several respondents who had initially reported adverse reactions indicated in writing that they were unwilling to reexamine their files and then reported no adverse reactions on the follow-up questionnaire. Psychiatrists saw more adverse LSD reactions than did any other professional group. These individuals described them as being bothersome at times, but they were not inclined to seek professional help.
Many people feel that adverse reactions to marihuana are relatively uncommon.
In addition, several respondents reported long-term personality changes from marihuana which they did not list as adverse reactions. Other drugs were not nearly so frequently mentioned as producing adverse reactions. A minimum of 2,389 adverse reactions to LSD were reported. For a number of reasons, this figure represents a conservative estimate of the total number of adverse reactions which actually occurred. The sampling methods employed contributed to a lesser number being reported.