Study: Marijuana use spikes in states where it's legal

It seems obvious, but we now have research to confirm it: Marijuana legalization has led to increased consumption among adults.

Why it matters: Research from the University of Colorado and University of Minnesota published this week provides some of the strongest evidence to date suggesting that legalization spurs more usage.

Adults in the 19 states where recreational marijuana is legal use it 24% more frequently than those living in states where it remains illegal, according to a news release from CU.

• The research was published in the journal Addiction, and studied 3,400 adult twins.

Of note: Researchers study twins because the pairs share genetics, tend to have similar socioeconomic statuses and community norms, providing well-matched controls.

Yes, but: Preliminary results from broader, ongoing studies indicate that increased usage isn't necessarily a bad thing, researchers say.

• Co-author and CU Boulder psychology and neuroscience professor John Hewitt said in a statement that increased use, "may be associated with less alcohol-related problems, and otherwise does not, in general, seem to have adverse consequences."

Flashback: Colorado in 2014 became the first place in the world to offer recreational marijuana sales, two years after voters statewide approved legalization.