detect DeltaFosB in the brain of 15 heroin addicts, nine days after they died.

Every major study focused on DeltaFosB has involved animal experiments under certain conditions, such as responses to conditions under cocaine exposure.

Seltenhammer’s study used human subjects and focused on opioid abuse, which is a growing problem around the world.

A 2001 animal study showed that DeltaFosB increased an animal’s sensitivity to cocaine and may represent a mechanism for prolonged sensitization not only to cocaine but to other drugs. The study also showed that DeltaFosB may also increase the propensity for relapse since it heightens the motivational properties of drugs.

“Thus, DeltaFosB may function as a sustained ‘molecular switch’ that helps initiate and then maintain crucial aspects of the addicted state,” researchers wrote. The protein also plays a role in behaviors toward food, sex, and exercise.

Dr. Eric Nestler, who led the 2001 animal study compared to a molecular switch. “Once it’s flipped on, it stays on and doesn’t go away easily.”