Stress can’t directly cause acne. However, if you already have acne, studies have shown that stress does make it worse. Researchers have also found that wounds, including acne, heal much slower when the sufferer is experiencing stress. Slower healing of acne means that the pimples stay around longer and are more susceptible to infection. This, in turn, leads to an increase in severity. It can also mean that more acne is visible at one time because it takes longer for each pimple to heal during a breakout.