Arrests for possessing small amounts of marijuana exceeded those for all violent crimes last year, a new study has found, even as social attitudes toward the drug have changed and a number of cities and states have legalized its use or decriminalized small quantities.

And a disproportionate number of those arrested are African-Americans, who smoke marijuana at rates similar to whites but are arrested and prosecuted far more often for having small amounts for personal use, according to the study. The arrests can overwhelm court systems.

Dianne Jones, 45, who was arrested in New Orleans in 2014 on charges of having a small bag of marijuana, spent 10 days in jail because she could not put up a $2,500 bond. She was able to get enough money together only after her daughter sold the family’s television set at a pawnshop for $200.

Later, when Ms. Jones, who is African-American, was unable to pay court-ordered fees and fines, a judge issued a warrant for her arrest.

With marijuana use on the rise, law enforcement agencies made 574,641 arrests last year for small quantities of the […]