Which of the following is a psychological sign of substance abuse?

Lack of motivation is a psychological sign of substance abuse because it can be indicative of an individual's diminishing interest in activities that were once important to them. Substance abuse often impacts a person's mental state, leading to alterations in mood, energy levels, and engagement with life. This lack of motivation may stem from the chemical changes in the brain caused by the substance itself, as well as the potential consequences of addiction, such as withdrawal symptoms or a preoccupation with obtaining or using the substance.

In the context of substance abuse, individuals may neglect responsibilities, lose interest in hobbies, or disengage from social interactions, all of which reflect a significant decline in motivation. These psychological changes can severely affect an individual's daily functioning and overall well-being.