Alcohol suppresses the activity of the prefrontal cortex and temporarily boosts serotonin, which can enhance mood and sociability while decreasing inhibition. However, as alcohol is metabolized, these effects diminish, leading to decreased mood and increased desire for more alcohol to regain the initial effects. Chronic alcohol use can lead to long-term changes in the neural circuits that control habitual and impulsive behaviors. These changes can persist even when not drinking alcohol, making individuals more impulsive and less inhibited over time. Fortunately, some effects can be reversed with abstinence over time. 

Regular alcohol consumption can lead to inflammation, hormonal imbalances, disrupted gut health and increased cancer risk in both men and women. Additionally, even moderate drinking (one to two drinks per day) has been linked to reduced cortical thickness and decreased gray matter volume in the brain. Historical studies have suggested some cardiovascular benefits of moderate alcohol consumption (like red wine), but recent research contradicts these claims, suggesting the safest approach is minimal to no alcohol intake. However, if you choose to drink, two drinks per week is considered the threshold beyond which negative health effects can occur.

Tobacco use, whether through cigarette smoking, vaping, snuffing or dipping, has significant negative health impacts. Using tobacco products increases blood pressure while reducing blood flow to organs and tissues (including the brain), and exposure to the dozens of carcinogens in tobacco products causes an increased risk of cancer, stroke, heart attack and cognitive decline.

While nicotine — the addictive component of tobacco — can enhance cognitive function and focus in the short-term, these benefits are outweighed by the severe long-term health risks associated with tobacco use. If using nicotine for cognitive performance, nicotine gum, lozenges or toothpicks can avoid many of the harmful effects linked to smoking or vaping. 

Quitting smoking can be challenging, but several methods have been found effective in aiding cessation. Using nicotine patches, gum, or nasal sprays (alone or in combination) can help manage withdrawal symptoms in order to gradually reduce nicotine intake over time. Clinical hypnosis has shown promise in enhancing the neural circuits that help maintain cessation, and medications like bupropion (Wellbutrin) can boost dopamine levels, which may also help offset withdrawal symptoms. The first week of withdrawal will be the toughest; use strategies like exercise and support from loved ones to reduce relapse risk.

Cannabis, commonly referred to as marijuana, contains a range of compounds that influence both the brain and body. The primary psychoactive component, THC (delta-9-tetrahydrocannabinol), is largely responsible for the plant's intoxicating effects. In contrast, cannabis also contains CBD (cannabidiol), a nonintoxicating compound that can impact mood and anxiety levels without inducing a “high.”

Cannabis has both potential benefits and risks. It's known to reduce pain and nausea, notably in chemotherapy patients, and might help with conditions like glaucoma. However, cannabis use can also have negative effects with chronic use, including increased anxiety, depression and risk of psychosis, especially in individuals with genetic risk factors. 

Oral consumption of cannabis (edibles) may be less harmful than smoking, as it avoids lung damage associated with inhaling combustible materials — however, it requires careful consideration of dosing and timing to avoid adverse effects. Vaporizing cannabis flower reduces exposure to harmful combustion byproducts when compared to smoking. At the same time, while the long-term effects of vaping are unknown, there are likely health risks.