However, when you want to compare a Boolean variable with the literal Boolean value true or false, it is not necessary to do an explicit comparison, because the result of evaluating a Boolean value is that Boolean value. For example, the expressions
The nicotine in cigarette smoke is a big part of the problem. It raises your blood pressure and heart rate, narrows your arteries and hardens their walls, and makes your blood more likely to clot. It stresses your heart and sets you up for a heart attack or stroke. Know Your Blood Pressure Numbers.
Recent research has shown how nicotine acts on the brain. Nicotine activates the circuitry that regulates feelings of pleasure, the so-called reward pathways. Research has shown that nicotine increases the levels of dopamine (a key brain chemical involved in mediating the desire to consume drugs) in the reward circuits of the brain. Nicotine's pharmacokinetic properties have been found to enhance its abuse potential. Smoking cigarettes produces a rapid distribution of nicotine to the brain, with drug levels peaking within 10 seconds of inhalation.