As an increasing number of states move to legalize cannabis for medical purposes, some people fear providing easier access to the drug will increase its recreational use as well. A study published by the Society for the Study of Addiction at the Institute of Psychiatry, Psychology, and Neuroscience details what research findings on cannabis, more commonly called marijuana, have revealed over the past two decades.

Tetrahydrocannabinol, or THC for short, is the substance in cannabis that produces the plant’s psychoactive properties. While researchers have studied the effects of cannabis for over half a century, the ability to ascertain the long-term effects of cannabis use has really only come to light in the last 20 years. This is due partially to improved study methods as well as the growing interest in calling for the drug’s legalization.

The Society for the Study of Addiction study details exactly how cannabis does and does not affect both the brain and the body in both short and long-term users. What the 20-year study made clear is that cannabis use can have a number of adverse effects for some people. What is not so clear is how science should be influencing policy as talk of legalization at the state level increases.

Effects of Cannabis

Increases in side effects of cannabis over the last 20 years are positively correlated with the increased levels of THC found in specially cultivated strains of the plant. It is the THC that leads to drug addiction in long-term use and can result in people requiring drug rehab. The acute, or short-term, effects of natural cannabis do not seem to be overly concerning, provided people treat it with the same respect as alcohol. However, synthetic cannabis use can be extremely dangerous.There are no known cases of a natural cannabis overdose and acute effects are generally limited to anxiety, dysphoria, cognitive impairment and paranoia. There also seems to be a link to some people developing psychotic symptoms, especially those with a family history of psychosis. Driving after using cannabis seems to increase the risk of an accident, especially if alcohol is already in the system. Cannabis has also been associated with low birth-weight delivery when taken during pregnancy.

Long-Term Use

The effects of using cannabis appear to become much more serious with long-term use. Here is what the Society for the Study of Addiction study found: • Long-term use can lead to addiction for some people. Approximately 10 percent of users appear to develop a dependence on the drug, and the number increases to about 15 percent for those who started using during adolescence. Withdrawal syndrome can lead to anxiety, appetite disturbance, depression and insomnia during detox.• Cannabis is linked to reduced attention levels, learning and memory problems. It isn’t entirely clear whether or not these issues persist once cannabis use is discontinued, but some evidence suggests it does. Some studies have found up to an eight-point reduction in IQ in long-time users, with the greatest decline being found in users who started as teenagers.• Long-term use may be linked to changes in brain function and structure. There has been an ongoing debate if cannabis use actually results in changes to the brain. New evidence does suggest that THC can cause changes to in the amygdala, hippocampus and prefrontal cortex. However, it is not clear how long these effects last and if the changes are reversed after detox.• Cannabis is linked to an increased risk of psychotic symptoms, including delusions, disorderly thinking and hallucinations.• The Society for the Study of Addiction found that cannabis is connected to an increased risk of schizophrenia. Schizophrenia is a psychological disordered caused by physiological charges in the brain. While previous studies have shown some evidence to suggest this connection, showing causality has proven difficult. However, the new study cites several other reputable studies that strongly suggest a causal relationship between cannabis use and schizophrenia.• Testicular cancer may be linked to cannabis use. While data connecting cannabis use to other types of cancer is not consistent, there is some fairly clear evidence that long-term cannabis use in men can increase their risk of developing testicular cancer.

• Regular cannabis users are at greater risk of developing cardiopulmonary issues. These can include chronic bronchitis and possibly emphysema. Marijuana use is known to cause tachycardia and hypertension, or high blood pressure.

While the long-term effects of cannabis use are becoming clearer, research should not be taken as trying to make a point for or against the legalization of cannabis. What the research does seem to show is there can be some possible serious consequences to cannabis use, especially with long-term use. As more states look to legalize the drug there also needs to be more emphasis placed on educating the public to the potential dangers of cannabis use, including drug addiction and the possibility of users requiring drug rehab.

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