Marijuana use, both for medical and recreational reasons, is becoming more acceptable in the United States. As of 2017, 26 states and the District of Columbia have legalized some form of marijuana use, mainly for medical purposes. While few medical users of marijuana smoke the drug, recreational use of cannabis has centered around smoking or vaping it for decades. Consuming a drug by smoking it can cause several long-term health problems, and marijuana use for a long time can also cause harm to the brain and body.

Are There Long-Term Effects from Smoking Marijuana?

Harm to the Brain

Several studies have shown that smoking marijuana, or otherwise abusing the drug, over several years can cause negative cognitive changes and harm mental health. A study referenced by the National Institute on Drug Abuse (NIDA) reported that a New Zealand-based study found that several people who began smoking marijuana in their teens, around age 13, lost eight IQ points by age 38 compared to people who had not abused the drug regularly.

A study published in the Journal of Neuroscience found that even smoking weed casually can change core structures in the brain linked to motivation, reward, and emotional regulation. The study followed people ages 18-25, some who smoked pot and some who did not. The groups differed in the size and density of the amygdala, which is involved in the stress response, and the nucleus accumbens, which is involved in the reward circuitry of the brain. Changing the structure of these parts of the brain may lead to addiction, abuse of the drug, greater frequency in the drug’s use, and anxiety or depression when the drug is not consumed. Even smoking occasionally led to these brain changes, although more drastic and permanent changes were seen in people who smoked pot more often.

Harm to the Brain

A paper published in the Proceedings of the National Academy of Sciences found that the orbitofrontal cortex (OFC) lost volume in people who smoked marijuana frequently. The study was adjusted for age and gender, and eliminated other drug use, so comparison between the control group and study group was more accurate. Those who abused marijuana had less neuronal connectivity, which may be connected to long-term pot use’s harm to memory formation, thinking, and decision-making skills.

People who smoke marijuana are also more likely to experience memory changes, and those who are at risk of psychiatric disorders like schizophrenia or psychosis are more likely to trigger these conditions; although the relationship may be inverse, as 23 percent of people who have schizophrenia abuse marijuana. A meta-analysis of several studies from 10 countries confirmed that consistent cannabis use was likely to influence anxiety or panic disorders. Abusing marijuana at least once per week increases the risk of developing depression 1.7 times while monthly abuse increases depression risk 1.4 times.

Heart Damage from Smoking Pot

People who smoke anything regularly, including marijuana, are at greater risk of causing harm to their cardiovascular system. Some studies have linked smoking weed to a greater risk of having a heart attack in middle age, although these studies were not large enough to be conclusive, and many of the people involved also smoked cigarettes.

A later study on cardiovascular disease associated with marijuana found that the annual risk of myocardial infarctions from consistent smoking increased from 1.5 percent to 3 percent per year. Because long-term pot use can also increase anxiety and panic disorder risk, hospitals have seen an increase in stress cardiomyopathy, a heart condition caused by increased stress. Between 2003 and 2011, hospitals across the nation saw 33,343 patients with stress cardiomyopathy, and an analysis of those patients found that 1 percent induced the condition through pot smoking. The analysis also found that pot smokers had weaker hearts, so 2.4 percent went into cardiac arrest compared to 0.8 percent of the non-smokers; and 2.4 percent were more likely to need correction for arrhythmias compared to 0.6 percent of non-users.

Ending Harm to the Body from Marijuana

Marijuana is very addictive and habit-forming, and long-term abuse of the drug causes damage to the body and brain. While cognitive and physical defects may be reversible, this requires abstinence from marijuana.