Which issue relates to poor function or incompetence due to substance use?

The issue that specifically pertains to poor function or incompetence due to substance use is impairment. Impairment means that a person's ability to perform tasks or job responsibilities is diminished due to the effects of substances—whether through intoxication, withdrawal, or other related issues. This concept encompasses the overall impact that substance use has on an individual's capability to effectively carry out their duties, thereby affecting their performance in the workplace.

While withdrawal, dependence, and abuse are all related to substance use in different ways, they do not capture the direct relationship to performance issues as clearly as impairment does. Withdrawal refers to the physical and psychological symptoms that occur when a person reduces or stops substance use, dependence denotes a psychological or physical condition where an individual feels a compelling need to use the substance, and abuse involves the harmful use of substances. Each of these aspects can lead to impairment, but impairment is the term that directly addresses the resulting impact on an individual's ability to function effectively in the workplace.