Researchers studied 15 heavy users compared to an age and IQ matched control group of non-smokers. We'll discuss their findings here. The study participants were not abusers of other drugs, nor did they exhibit any co-existing psychiatric conditions. Research found that heavy marijuana smokers had smaller tissue volume in the hippocampus and amygdala of the brain, but not in other major areas. This shows the damage is central to the mediotemporal lobe, which is involved in both the initial learning of facts and events and their later consolidation.
The hippocampus and amygdala, part of the limbic system and otherwise known as the “emotional brain,” are in charge of regulating memory, stress response, sleep, appetite, motivation, social cognition, fear and anger. This includes both episodic memory, which is the memory of specific events, and spatial memory, which is the general awareness of the surrounding environment. People who have suffered damage to these areas sometimes have a tendency to suffer from anxiety and panic attacks, physical ailments relating to stress, trouble retaining information, recalling older memories, and building new ones. They may also exhibit uncontrolled risk taking.
What's interesting in comparison to this study is that dysfunction in the limbic brain system has been seen in a number of diseases, consisting of anxiety disorders, dementia, and schizophrenia, as well as bipolar disorder and clinical depression. Previous studies on marijuana use outside of this one have shown similar neurological deficiencies for those heavy users when receiving treatment for marijuana abuse. We also know that quitting marijuana after a period of heavy use can lead to many side effects, including anger, anxiety, appetite changes, depression, stress leading to physical problems, and sleep disturbances.