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    Differential Diagnosis
    What is It and Why is It Important?

    Are your loved one’s concerning thoughts, emotions and behaviors the result of a mental health disorder, a substance use disorder, or both? Often mental health and substance use symptoms mimic each other so it can be tricky to make a diagnosis. When seeking help, your loved one’s healthcare provider uses the diagnostic process to determine what condition may be causing their symptoms.  Figuring this out is called a differential diagnosis. Determining the right diagnosis is important because treatment for a mental health disorder can be very different from treatment for a substance use disorder. And if both disorders are present, co-occuring treatment is needed.

    What's causing these symptoms?

    You may not have all the necessary information about your loved one’s situation, which can make it more difficult to get the proper treatment.

    For example, you may be concerned about mood swings and suspect your loved one has bipolar disorder. Instead, their mood swings may be from using opioids and cocaine. Similarly, you may be concerned about a loved one’s use of alcohol when the real problem is anxiety or trauma.

    Finding the right treatment is more difficult when loved ones don’t report everything that is going on in their lives. When they seek help for mental health problems, they may be reluctant to talk about their substance use. Similarly, loved ones being evaluated for substance use 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 very important for healthcare providers to get a full picture of your loved one’s symptoms and their use of substances, if any. You can help encourage your loved one to talk about what’s truly going on in their life and help fill in the gaps as well. You can share information about their history, the family’s history and other factors, such as recent problems (e.g., missing school or work, changes in sleep or eating patterns, use of substances, etc.).

    Getting an Evaluation

    A differential diagnosis depends on reports from your loved one, your family, teachers in the case of teens, other doctors and the healthcare provider’s observations. Tests may be used such as a urine screen to get a picture of recent substance use. Blood tests may be used to rule out physical problems that may be causing symptoms. This picture of what’s happening is used to help form a diagnosis.

    Here are some examples of questions a healthcare provider may ask:

    • What kind of symptoms are you experiencing? When did they begin?
    • What makes your symptoms better or worse?
    • Is your sadness related to a loss, or just out of the blue?
    • What role do alcohol and other drugs play in your life?
    • Is there a family history of mental health problems and/or addiction?
    • Is your impulsivity a part of your personality, tied to being hyper, or is it more manic and self-destructive?
    • What major events or stressors have you faced?

    Key Takeaways

      Mental health symptoms can mimic the effects of substance use and vice versa.


      Loved ones with mental health problems may be reluctant to talk about their substance use.


      Effective treatment requires a detailed evaluation.


      It is critical for healthcare providers to talk with family and others (e.g., teachers, other providers) to get a full picture in order to develop the right treatment plan.

    Examples of results

    Differential diagnosis may show that substance use is a consequence of a mental health disorder. Here are just a few examples:

    • Alcohol can be a a way of coping with 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 stress related to academic or work performance.

    On the other hand, mental health symptoms could result from the direct effect of the use of substances. Again, here are just a few examples of what can occur:

    • 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 loved one’s substance use and mental health symptoms are not directly related to each other, they can still make each other worse.

    How do I find a healthcare professional who can do an evaluation?

    To obtain an evaluation and get a diagnosis, it’s important to find a mental healthcare provider who has specialized training and experience in this area.  Your loved one’s primary care physician can be a good starting point. They may be able to recommend a psychiatrist, psychologist or addiction specialist or you may be able to locate one through local medical associations. If you have health insurance, contact your insurance provider to ask for recommendations and find out which mental health and addiction treatment providers are in-network. This can help you manage costs.

    Ask for recommendations from your friends, family or support groups. People who have gone through similar experiences may be able to provide valuable insights into reputable professionals in your area.

    Regardless of the type of professional you choose, make sure they are licensed and certified in their respective fields. You can verify their credentials through state licensing boards or professional associations.  Before committing to a specific professional, schedule initial consultations or interviews with a few of them. Ask about their experience with co-occurring disorders, their treatment approach and how they coordinate care with other specialists if needed.

    Ultimately, your loved one should feel comfortable and confident in their healthcare provider. Trust your instincts and choose someone with whom you think they can establish a strong therapeutic relationship.