Differential Diagnosis

What’s Causing These Symptoms?

Are your child’s concerning thoughts, emotions and behaviors the result of a mental health disorder or a substance use disorder? Figuring out which symptoms come from which disorder, and which problem started first, is called differential diagnosis. Determining differential diagnosis is important, because treatment for a mental health disorder can be very different from treatment for a substance use disorder.

You may be concerned about mood swings and suspect your child has bipolar disorder, when in fact he or she has been using opioids and cocaine. Similarly, a child could be diagnosed with a cannabis (marijuana) use disorder without considering that there may be something else going on or at the root of the issue, like anxiety or a traumatic experience.

Finding the right treatment becomes complicated when adolescents or young adults don’t report everything that is going on in their lives. When young people are referred for help for a mental health disorder, they often can be reluctant to talk about their substance use. Similarly, young people being evaluated for substance use problems will often avoid discussing emotional or behavioral problems.

This lack of information can make it hard to get an accurate diagnosis. That’s why it is critical for clinicians to get a full picture of what symptoms occurred first and when substance misuse began. You can help encourage your child to talk about what’s truly going on in his or her life, and help fill in the gaps, as well. You can share information about your child’s and family’s history as well as other factors, such as recent problems (e.g., missing school, changes in sleep or eating patterns, etc.).

Behavioral symptoms that can result from both mental health disorders and substance use include:

  • Moodiness
  • Sleeping more or less than usual
  • Paranoia
  • Avoiding friends and situations
  • Erratic behavior

Getting an Evaluation

There are no laboratory tests to diagnose mental health or substance use disorders, so differential diagnosis depends on reports from the patient, his or her family, teachers and other doctors, and the clinician’s observations. This picture of what’s happening is then compared to criteria in the DSM-5, which professionals use to help diagnose.

Here are some examples of questions a clinician tries to answer:

  • Is sadness related to a loss, or just out of the blue?
  • Is the adolescent using substances as a way of coping?
  • Is substance use a response to stressful life events?
  • Is impulsivity part of a child’s personality, or tied to hyperactivity, or is it more manic and self-destructive?
  • Is the goal of substance use to seek excitement or to escape reality?

Examples of Results

Differential diagnosis may reveal that substance use is a consequence of a mental health disorder. Here are just a few examples of how substance use can grow out of a mental health disorder:

  • Alcohol can be a self-treatment for anxiety, depression or bipolar disorder.
  • Marijuana use is often tied to psychotic disorders, ADHD and anxiety.
  • Opiates (Percocet, Tylenol w/Codeine) and benzodiazepines (Xanax, Ativan) are more likely to be used by young people with oppositional defiant disorder, conduct disorder and borderline personality disorder.
  • Amphetamine (Adderall) use can be a response to overwhelming anxiety and stress related to academic performance.

On the other hand, psychiatric mental health symptoms might result from the direct effect of the substance on the brain. Again, here are just a few examples:

  • Alcohol use can cause significant mood fluctuations.
  • Nicotine use can mimic anxiety symptoms.
  • Psychedelic drugs can cause psychotic states.

Even if it turns out that a young person’s substance use and mental health symptoms are not related to each other, they can still make each other worse.

The next few sections introduce adolescent mental health disorders, their symptoms and treatment, and substance issues that commonly co-occur with these disorders.