As the brain ages, our thinking organ shrinks. Now a new study claims to have pinpointed important factors in what makes the brain age faster. The study is published in the Journal of Alzheimer's Disease.

The study was carried out by Johns Hopkins University, the Universities of California, Los Angeles and San Francisco, Google, and Amen Clinics, headed up by the somewhat controversial celebrity psychiatrist Daniel Amen.

The study looked at over 62,000 brain scans of more than 31,000 people, both while resting and during a concentration task, using the SPECT (single photon emission computed tomography) scan imaging technique. SPECT is a nuclear medicine technique that uses gamma-rays to help scientists reconstruct 3D images of the brain. Amen used this to map the blood flow around the brain. In the study, he used scans from individuals as young as 9 months up to 105 years to investigate what factors might accelerate brain aging, and which "common" brain disorders predict abnormally accelerated aging. The study concludes that conditions like schizophrenia, bipolar disorders, ADHD, cannabis abuse, and alcohol abuse all contribute to this acceleration.

“Based on one of the largest brain imaging studies ever done, we can now track common disorders and behaviors that prematurely age the brain," Amen said in a statement. "Better treatment of these disorders can slow or even halt the process of brain aging.”

Obviously, everybody's brain ages, whether you have those conditions and behaviors or not. Being able to halt the process of brain aging altogether wouldn’t be only important for people suffering from dementia and Alzheimer’s disease, it would change the life of each and every human being. 

However, the study states that the "subjects were drawn from multiple branches of the 92 Amen Clinics", undergoing treatment for a number of disorders, and there is little to no information on a control sample of healthy brains, so it is unclear what conclusions can be drawn about the human brain in general from the results. 

The researchers looked at 128 regions of the brain in an attempt to predict the chronological age of the participant, based on blood flow around the brain. If older age was predicted by the scan than the patient's actual age, this was deemed accelerated aging. However, it is unclear how the scans of the cerebral blood flow indicate the estimated age, or if these predictions stood up to a control sample. While psychological conditions certainly can play a role, it has been shown in the past that heart problems, and thus dietary and lifestyle habits, play an important role as well.

The study concludes that the brain scans' prediction of age for certain people who display particular brain or behavioral disorders, such as schizophrenia or cannabis abuse, is on average higher than their actual age, and thus these can be used as predictors of accelerated brain aging. Certain conditions and behaviors have already been proven to play a key role in brain aging, of course, but the underlying effects at play in our brain cannot be determined by a single factor.