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.
6.3 Psychoactive effects of nicotine. In addition to the physical effects outlined in the previous section, nicotine also has acute effects on a smoker's mental state. Nicotine has biphasic brain effects, that is, it can improve alertness by stimulating brain function and also produce a feeling of relaxation by depressing functioning.