Final answer:
Marijuana's adverse effects on public perception and legality stem from early 20th-century xenophobia, misinformation campaigns, and subsequent legal restrictions. Recent shifts in attitude towards marijuana are due to a better understanding of its effects, recognition of disproportionate penalties across races, and acknowledgment of its potential medical benefits.
Step-by-step explanation:
What adversely affected the perception and legality of marijuana? Over time, marijuana has faced various forms of stigmatization and legal challenges. In the early 20th century, a blend of xenophobia, competition for jobs, and fear-mongering began to paint marijuana as a dangerous and deviant substance. Police and media outlets circulated myths about its alleged link to violence and immorality, leading to state and federal prohibitions beginning in 1916 and culminating with a federal law in 1937. Alongside this, long-term health concerns related to marijuana, like problems with brain development and respiratory issues, contributed to its negative image.
However, recent years have seen a shift in public opinion regarding marijuana legalization and its effects. This change can largely be attributed to a more informed understanding of cannabis, acknowledgment of racially skewed penalties for its possession, and the potential medical benefits despite federal restrictions on research. This evolution of thought reflects in the movement for the decriminalization and legalization of marijuana, contrasting sharply with past portrayals of cannabis users.