Long Term Effects of Marijuana

Flowering Marijuana Plant
Photo by: purplequeue/Shutterstock

Although marijuana has only recently become legal and in only a few states, people have been smoking it for years. Many feel they have had little reaction to their extended use, however, studies have shown that over time there are some adverse effects from years of marijuana consumption.

A recent study showed that users of marijuana who started smoking in their youth considerably lowered the connectivity within brain areas liable for learning and storing memory.

Where Research Points

In a larger long-term study in New Zealand, people, from the ages of 13 and 38, who began using cannabis heavily in their adolescence, missed, on average, 8 points in IQ tests. More importantly, the lost cognitive abilities were not completely returned in those who quit smoking marijuana in adulthood. Those who started smoking marijuana in adulthood did not show substantial IQ declines.

Marijuana raises the heart rate from about 20-100 percent not long after smoking, so there is some risk of heart attack, especially in those who are older or have cardiac problems.

Though this risk is small, there is great danger in use of cannabis when mental illness is present, particularly schizophrenia, where inhaling the drug may worsen the disease. Although more studies need to be made to understand and confirm, links have been made between marijuana use and mental health problems such as anxiety, depression, lack of motivation, suicidal thoughts in teens, and personality disturbances.

Dosage is Everything

High doses of the drug can yield a temporary psychotic reaction (involving hallucinations and paranoia) in some users. A series of large studies following users also indicated a link between marijuana use and later development of psychosis in life.

Though this connection was influenced by genetic variables as well as the amount of drug used, drug potency, and the age at which marijuana was first introduced those who begin smoking at a young age have a higher chance of problems in adulthood.

Not only does marijuana affect the brain, but it has proven as well to be an irritant to the lungs. Not unlike cigarette users, smoking cannabis can cause some of the problems such as a daily cough and phlegm production, more recurrent chest illness, and a higher risk of lung infections.

However, it is not yet known whether marijuana smoking contributes to the risk of lung cancer as it does with tobacco use.