What is a common symptom indicating drug or alcohol use in the workplace?

Decreased productivity is a common symptom that can indicate drug or alcohol use in the workplace because substances can impair an individual's ability to perform tasks effectively and efficiently. When a person is under the influence, their focus, coordination, and decision-making skills may be compromised, leading to mistakes or slower work output. This can ultimately affect not only the individual's performance but also the overall productivity of the team or organization. Recognizing decreased productivity as a symptom is critical for employers and co-workers, as it may lead to further investigation or support for the individual in question.

In contrast, the other options present scenarios that are generally not associated with substance use. For example, decreased absenteeism and improved interpersonal interactions would more likely indicate positive engagement with work, while clear speech is typically an indication of someone who is sober and coherent.