How is smoking, Alcohol and drug abuse detrimental to a healthy lifestyle?

Smoking

Chemicals in tobacco smoke increase the chance of heart problems and cardiovascular diseases.

Smoking causes atherosclerosis, which is when plaque builds up in the blood and sticks to the artery walls. This makes them narrower, reducing blood flow and increasing the risk of blood clots.

Smoking also damages the blood vessels, making them thicker and narrower. This makes it harder for blood to flow, and also increases blood pressure and heart rate.

Smoking has links with the following cardiovascular conditions:
coronary heart disease, one of the leading causes of death in the U.S
a heart attack, as smoking doubles the risk of heart attack
blockages that reduce blood flow to the skin and legs
stroke due to blood clots or burst blood vessels in the brain

Even smokers who smoke 5 or fewer cigarettes a day may develop early signs of cardiovascular disease.

Carbon monoxide and nicotine make the heart work harder and faster. This means that smoking makes it more challenging to exercise. A lack of exercise further increases the risk of health problems.

Alcohol

Drinking can cause a number of health problems and is associated with over 200 diseases and injury-related conditions. Studies have shown that one drink a day increases the risk of breast cancer in women. Research has also shown that alcohol misuse increases the risk of liver disease, cardiovascular diseases, depression, and stomach bleeding, as well as cancers of the oral cavity, esophagus, larynx, pharynx, liver, colon, and rectum. They may also have problems managing conditions such as diabetes, high blood pressure, pain, and sleep disorders. And they are more likely to engage in unsafe sexual behavior, putting themselves and others at risk for sexually transmitted diseases and unintentional pregnancies.

Drug abuse

Drugs contain chemicals that tap into the brain’s communication system and disrupt the way nerve cells normally send, receive, and process information.

Some drugs (e.g., marijuana and heroin) have a similar structure to chemical messengers called neurotransmitters, which are naturally produced by the brain. This similarity allows the drugs to “fool” the brain’s receptors and activate nerve cells to send abnormal messages.

Other drugs, such as cocaine or methamphetamine, can cause the nerve cells to release abnormally large amounts of natural neurotransmitters (mainly dopamine) or to prevent the normal recycling of these brain chemicals, which is needed to shut off the signaling between neurons. The result is a brain awash in dopamine, a neurotransmitter present in brain regions that control movement, emotion, motivation, and feelings of pleasure. The overstimulation of this reward system, which normally responds to natural behaviors linked to survival (eating, spending time with loved ones, etc.), produces euphoric effects in response to psychoactive drugs. This reaction sets in motion a reinforcing pattern that “teaches” people to repeat the rewarding behavior of abusing drugs.

As a person continues to abuse drugs, the brain adapts to the overwhelming surges in dopamine by producing less dopamine or by reducing the number of dopamine receptors in the reward circuit. The result is a lessening of dopamine’s impact on the reward circuit, which reduces the abuser’s ability to enjoy the drugs, as well as the events in life that previously brought pleasure. This decrease compels the addicted person to keep abusing drugs in an attempt to bring the dopamine function back to normal, except now larger amounts of the drug are required to achieve the same dopamine high—an effect known as tolerance.

Long-term abuse causes changes in other brain chemical systems and circuits as well. Glutamate is a neurotransmitter that influences the reward circuit and the ability to learn. When the optimal concentration of glutamate is altered by drug abuse, the brain attempts to compensate, which can impair cognitive function. Brain imaging studies of drug-addicted individuals show changes in areas of the brain that are critical to judgment, decision-making, learning and memory, and behavior control. Together, these changes can drive an abuser to seek out and take drugs compulsively despite adverse, even devastating consequences—that is the nature of addiction.