Mixed Findings on Pot's Effect on the Developing Brain
Mixed Findings on Pot's Effect on the Developing Brain
By Dennis Thompson
HealthDay Reporter
WEDNESDAY, Aug. 26, 2015 (HealthDay News) -- Marijuana's potential effect on brain structure remains a subject of intense scientific scrutiny, but mixed results have emerged from two of the latest studies on the topic.
Researchers in one study have concluded that marijuana use likely does not directly affect the size of the amygdala, a brain site linked with emotion, emotional behavior and motivation.
"We found that while cannabis users had lower amygdala volumes than nonusers, that difference appears to be linked to other predisposing factors," said senior author Arpana Agrawal, an associate professor of psychiatry at Washington University School of Medicine in St. Louis.
But researchers in the other study found that marijuana use in the teenage years could increase kids' risk for developing schizophrenia if they carry a high genetic risk for the mental illness.
"If there is a family history of severe psychotic disorders, I would really encourage kids to avoid cannabis altogether," said senior author Dr. Tomas Paus, a senior scientist at the Rotman Research Institute in Toronto. "If you know these disorders run in your family, then I would be super, super careful."
Both studies were published Aug. 26 in JAMA Psychiatry.
In Agrawal's study, researchers performed brain scans on more than 480 twins or siblings as young adults, 262 of whom reported they'd used pot at least once.
Marijuana users were found to have smaller amygdalas than nonusers, a result that agreed with earlier findings, Agrawal said.
But researchers found that brain volumes did not differ significantly between twins or siblings, even if one had used marijuana and the other had not, she said. Both siblings showed smaller amygdalas, regardless of pot use.
Based on this, common genetic factors might influence amygdala size as well as one's propensity to experiment with marijuana, Agrawal said.
Some environmental factor could also be at play, she added. For example, childhood exposure to adversity can affect amygdala size, and also can make a person more likely to try drugs.
In the other study, researchers drew brain scans and data from three other large-scale studies, amassing a pool of nearly 1,600 participants, ages 12 to 21.
HealthDay Reporter
WEDNESDAY, Aug. 26, 2015 (HealthDay News) -- Marijuana's potential effect on brain structure remains a subject of intense scientific scrutiny, but mixed results have emerged from two of the latest studies on the topic.
Researchers in one study have concluded that marijuana use likely does not directly affect the size of the amygdala, a brain site linked with emotion, emotional behavior and motivation.
"We found that while cannabis users had lower amygdala volumes than nonusers, that difference appears to be linked to other predisposing factors," said senior author Arpana Agrawal, an associate professor of psychiatry at Washington University School of Medicine in St. Louis.
But researchers in the other study found that marijuana use in the teenage years could increase kids' risk for developing schizophrenia if they carry a high genetic risk for the mental illness.
"If there is a family history of severe psychotic disorders, I would really encourage kids to avoid cannabis altogether," said senior author Dr. Tomas Paus, a senior scientist at the Rotman Research Institute in Toronto. "If you know these disorders run in your family, then I would be super, super careful."
Both studies were published Aug. 26 in JAMA Psychiatry.
In Agrawal's study, researchers performed brain scans on more than 480 twins or siblings as young adults, 262 of whom reported they'd used pot at least once.
Marijuana users were found to have smaller amygdalas than nonusers, a result that agreed with earlier findings, Agrawal said.
But researchers found that brain volumes did not differ significantly between twins or siblings, even if one had used marijuana and the other had not, she said. Both siblings showed smaller amygdalas, regardless of pot use.
Based on this, common genetic factors might influence amygdala size as well as one's propensity to experiment with marijuana, Agrawal said.
Some environmental factor could also be at play, she added. For example, childhood exposure to adversity can affect amygdala size, and also can make a person more likely to try drugs.
In the other study, researchers drew brain scans and data from three other large-scale studies, amassing a pool of nearly 1,600 participants, ages 12 to 21.
