Cannabis and alcohol abuse accelerate brain aging, according to what is thought to be the largest brain imaging study ever conducted.

“The cannabis abuse finding was especially important, as our culture is starting to see marijuana as an innocuous substance,” said the paper’s lead author, psychiatrist Daniel G. Amen, M.D. “This study should give us pause about it.”

Amen is the founder of Amen Clinics in Costa Mesa, CA, which participated in the evaluation of 62,454 brain SPECT (single photon emission computed tomography) scans of more than 30,000 people aged nine months to 105 years to investigate factors that accelerate brain aging. Other scientists involved in the study came from Google, John’s Hopkins University, Baltimore; the University of California, Los Angeles; and the University of California, San Francisco.

The researchers found that several brain disorders and behaviors predicted accelerated aging, especially:

  • Schizophrenia, which showed an average of 4 years of premature aging;
  • Cannabis abuse (2.8 years);
  • Bipolar disorder (1.6 years);
  • Attention-deficit/hyperactivity disorder (1.4 years); and
  • Alcohol abuse (0.6 years).

Investigators did not observe accelerated aging in depression and aging, which they hypothesize may be due to different types of brain patterns for those disorders.

The study will appear in an upcoming issue of the Journal of Alzheimer’s Disease.