Answer: False
Step-by-step explanation:
The American Psychiatric Association (APA) does not classify the severity of a substance use disorder based on the number of substances a person uses. The severity of a substance use disorder is typically determined by various factors, such as the impact of the disorder on a person's functioning, the intensity of cravings, withdrawal symptoms, and other diagnostic criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) published by the APA.