President Nixon requested:

THE SHAFER COMMISSION REPORT (1972)

Which states:

“No significant physical, biochemical, or mental abnormalities could be attributed solely to marihuana smoking… No valid stereotype of a marihuana user or non-user can be drawn…

• Young people who choose to experiment with marihuana are fundamentally the same, socially and psychologically, as those who use alcohol and tobacco…
• No verification is found of a causal relationship between marihuana use and subsequent heroin use….
• Most users, young and old, demonstrate an average or above-average degree of social functioning, academic achievement, and job performance…”

“The weight of the evidence is that marihuana does not cause violent or aggressive behavior; if anything marihuana serves to inhibit the expression of such behavior…

• Marihuana is not generally viewed by participants in the criminal justice community as a major contributing influence in the commission of delinquent or criminal acts…
• Neither the marihuana user nor the drug itself can be said to constitute a danger to public safety… 
• Research has not yet proven that marihuana use significantly impairs driving ability or performance…”

“No reliable evidence exists indicating that marihuana causes genetic defects in humans… Marihuana’s relative potential for harm to the vast majority of individual users and its actual impact on society does not justify a social policy designed to seek out and firmly punish those who use it.”