Modafinil and Adderall both have stimulant-like effects. But the significant differences in their structure translate to massive differences in their addiction potential and risk of side effects.

• Modafinil and Adderall both have stimulant-type effects, although modafinil is not classed as a stimulant.
• Modafinil improves wakefulness and decision making but does not make you any smarter.
• Adderall is also much more likely than modafinil to cause addiction and dependence and withdrawal symptoms on discontinuation, in addition to more side effects, without improving IQ.
• Neither drug should be taken with alcohol and both have the potential to adversely affect the heart.

Differences in Structure and Uses, Similarities in Effects

Modafinil (Provigil) has a unique structure and is not a stimulant like Adderall, but it does have stimulant-like effects and improves alertness, enhances thinking and perception, in addition to helping to keep people awake. Experts aren't exactly sure how it works, although they have elucidated that it enhances several chemicals and neurotransmitters in the brain including dopamine, serotonin, histamine, glutamate, and GABA. Although studies have not shown any significant withdrawal effects, any drug that provides stimulant effects to the brain enforces drug taking to some extent and carries the potential for dependence which could lead to withdrawal symptoms. Anecdotally people have reported significantly reduced energy, lack of motivation, and depression following discontinuation of Provigil. Modafinil should always be tapered on drug discontinuation if it has been used for a long period of time.

Modafinil was first approved by the FDA in 1998 to treat narcolepsy, and is also used to treat excessive sleepiness caused by obstructive sleep apnea (OSA) or shift work. Off-label it has been used to help people with Parkinson's Disease and Multiple Sclerosis stay alert, and has been favored by students, executives, and the military as a way to combat sleep deprivation and fatigue. Even though it is not approved for ADHD, it is often used and at least one study has suggested it helps reduce symptoms of impulsivity in those with ADHD.

Adderall is the brand (trade) name for a combination tablet containing amphetamine and dextroamphetamine (often called mixed amphetamine salts). Adderall is usually prescribed to treat people with narcolepsy or ADHD. Adderall has also become one of the more popular illicit "study-aids" or party drugs with almost 7.5% of high school seniors and one-third of college undergraduates reportedly misusing the drug. Adderall is a stimulant that increases the concentration of dopamine and norepinephrine in the brain. Its exact mechanism of action in ADHD or narcolepsy is not known. Adderall was first approved for ADHD in 1996 and for narcolepsy in 1998.

Which has the most side effects?

Side effects experienced with modafinil are generally mild compared to those reported with Adderall, although modafinil can significantly increase heart rate and blood pressure and should not be taken by people with a history of certain heart or heart valve problems (such as mitral valve prolapse or left ventricular hypertrophy). Over one-third of people who take modafinil report headache as a side effect, with nausea being the next most common complaint (11% of people taking modafinil). Other side effects such as rhinitis, nervousness and anxiety, back pain, insomnia, and gastrointestinal complaints (such as diarrhea, indigestion) were reported by less than 10% of clinical trial participants.

Modafinil can reduce the effectiveness of hormonal contraceptives - both estrogen and progestogen-containing oral and implantable products, by interfering with the enzymes that convert the hormones into their active form.

Rarely, life-threatening rashes have occurred with modafinil, including Stevens-Johnson Syndrome (SJS) and drug-induced hypersensitivity syndrome (DRESS). Most reactions are probably allergy related. Although modafinil has been around for over 20 years, experts are not sure how long-term use affects the brain. Some are concerned about chronic sleep deprivation, future ability to sleep, increased antisocial tendencies and a suppressing of emotions, as well as problems coming off the drug.

Adderall tends to have a broader range of side effects; some people will experience certain side effects more severely than others. The most common side effects include loss of appetite (36%), dry mouth (35%), short-lived blood pressure elevations (up to 35%), insomnia (up to 27%), headache (up to 26%) and abdominal pain. Disturbances in sexual function, a slowing of the growth rate in children, fast heart rate, and nervousness are also commonly reported.

Some people are overly sensitive to stimulants and develop confused thought processes, regardless of what dosage they take. Psychiatric side effects reported with Adderall include hearing voices, becoming suspicious for no reason, or becoming manic. Adderall can also exacerbate symptoms in people already suffering the effects of psychotic disorder or bipolar illness.

It should also not be used by people with glaucoma, an overactive thyroid, heart disease or moderate to severe high blood pressure, or a history of drug or alcohol addiction. One of the main problems with Adderall is that it may cause dependence and tolerance and be subject to abuse. If Adderall is suddenly stopped, it may cause a withdrawal syndrome (symptoms include extreme tiredness, depression, and sleep disturbances).

Modafinil is a Schedule IV controlled substance and Adderall is a schedule II controlled substance - reflecting its higher propensity for abuse and dependence.

Neither Should Be Taken With Alcohol

Neither modafinil nor Adderall should be mixed with alcohol. Even though modafinil and Adderall are both stimulating and alcohol is a depressant, taking them together does not cancel each other one out; rather it sends the brain mixed messages. People have reported blacking out after only minor amounts of alcohol while taking modafinil, and some people who have only taken one dose of Adderall mixed with one drink have ended up in hospital.

Both modafinil and Adderall can affect the heart and blood pressure and mixing them with alcohol increases the potential of arrhythmias and other heart complaints.

Do they really make you smart?

Several small trials have tried to determine if Modafinil really does enhance cognition, with mixed results. Participants reported feeling more alert, attentive and energetic on the drug, in one 2003 trial, and some improvements in certain memory tasks - such as digit span and visual recognition - were reported. In addition, there was a decrease in impulsivity. A 2014 trial also showed improvements in impulsive decision making, but no difference in the accuracy of performance.

Modafinil was found to enhance attention and learning and improve decision making and planning in a review of 24 studies. However, it made no difference to working memory or understanding different points of view and negatively affected creativity in a few studies.

Adderall has been used as a study aid based on the assumption that stimulants used for ADHD help reduce hyperactivity, impulsivity, and inattention. However, there are very few trials investigating whether Adderall does enhance cognition in individuals without ADHD. Results were conflicting, with some studies showing no effect, and others showing minor improvements; some even showed a negative effect. While Adderall may promote wakefulness, it does not improve IQ. Any short term gains in alertness are overwhelmingly counteracted by withdrawal symptoms and potentially fatal side effects.

Use in Combat

Modafinil has been used to optimize performance in sleep-deprived soldiers, pilots, and also fatigued astronauts. In 2012, modafinil replaced dexamphetamine (a component of Adderall) as the military's "go-pill". Studies have shown it helps maintain alertness, improves judgment, cognitive function, feelings of well-being, and increases risk perception and situation awareness. Side effects in one study of six helicopter pilots included vertigo, nausea and dizziness.

More Information

• Drugs.com Compare Tool - Adderall vs Modafinil
• Modafinil: Smart Drug For Decision Fatigue Or Workaholic Crutch?
• Adderall for study: Does it really make you smarter?