New York ? Chronic cocaine use harms brain circuits that help produce the sense of pleasure, which may help explain why cocaine addicts have a higher rate of depression, a study suggests.

It’s not clear whether cocaine kills brain cells or merely impairs them, or whether the effect is reversible, said study author Dr. Karley Little. But it’s bad news for cocaine addicts in any case, he said.

“I personally wouldn’t want to lose 10 or 20 percent of my reward-pleasure center neurons or have them just deranged or not working right,” said Little, of the Ann Arbor, Mich., Veterans Affairs Medical Center and the University of Michigan.

The research provides “a piece of the puzzle” in explaining why cocaine users run a higher risk of depression, said neuroscientist Dr. Deborah Mash.

It remains unclear whether cocaine causes depression or whether people start using the drug because they are depressed. But in either case, Mash said, the study suggests brain changes could “light the fuse” for depression in a cocaine user who is prone to it.