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Effects & Side Effects of Stimulants

By Jacques Courseault ; Updated August 14, 2017

Stimulants are commonly used on a daily basis to increase energy, motivation and mental alertness. In general, stimulants work to increase certain chemical signals in your brain that enhance the activity of the central nervous system. Stimulants are found in prescribed medications, in common products such as coffee and cigarettes, and as illegal street drugs. Whether a stimulant is prescribed or not, you should be aware of its possible effects and side effects.


A 2004 Johns Hopkins study indicated that caffeine in the form of coffee, tea, soft drinks, chocolate and energy drinks is consumed by more than 90 percent of Americans. Caffeine has the effect of reducing drowsiness and increasing alertness by stimulating the brain, according to Dizziness, irritability, nausea and nervousness are also noted side effects.

Additionally, the Johns Hopkins study suggested that severe withdrawal can occur with abrupt discontinuation of caffeine use. A severe headache was noted 12 to 24 hours after discontinuation of caffeine use in 50 percent of the study participants. However, when consumed in moderation, the side effects of caffeine are not problematic.


Nicotine is a stimulant found in cigarettes, cigars and other tobacco products. According to a 2008 article in "Clinical Pharmacology and Therapeutics," nicotine causes euphoria and relaxation by increasing neurotransmitters in the part of the brain that responds to reward and causes addiction.

While nicotine may increase alertness and arousal, there are significant side effects associated with smoking. According to the U.S. Center for Disease Control (CDC), smoking causes 90 percent of lung cancer deaths in men and significantly increases the risk of death from chronic obstructive pulmonary disease in all smokers. Nicotine can also cause seizures, chest pain, or irregular heartbeat, according to


Amphetamines are prescribed by doctors for attentional deficit disorder, narcolepsy, obesity and other medical problems. Some effects of amphetamines include euphoria, alertness, increased concentration and increased feelings of power, according to Psychology Today (see Resources below).

Constipation, diarrhea, trouble sleeping, dizziness, dry mouth, headache, nausea, stomach ache, nervousness, restlessness and loss of appetite are common side effects, according to If you experience these side effects, speak with your doctor about how to alleviate them.

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