Differential diagnosis, part one: when the body or a substance is the cause

Transcript

SoheeTwo months ago, a 40-year-old construction worker fell at a job site and hit his head. He went to the emergency room, was sent home, and never had a follow-up visit.

RyanNow he's been referred to a psychologist for low mood, irritability and trouble concentrating.

SoheeAnd on paper, that could look like the start of a depressive disorder. But there's a fall, and a head injury, sitting right there in the history.

RyanWelcome to EPPP Prep, the podcast. I'm Ryan.

SoheeI'm Sohee. This is the first of two episodes on differential diagnosis. The knowledge statement pairs it with something specific: the integration of non-psychological information into psychological assessment. Today that means the body, medications, and substances.

RyanA quick note on our sources. For diagnosis, we're using the public condition summaries from SAMHSA, the federal Substance Abuse and Mental Health Services Administration, plus the OpenStax psychology textbook.

SoheeLet's start with depression. SAMHSA's depression page says, plainly, that some tests are used to rule out other serious medical conditions that may cause similar symptoms.

RyanAnd it names what raises the risk of depression in the first place: a family history of depression, trauma, major life changes, stress, certain physical illnesses such as diabetes, cancer or Parkinson's, and side effects of certain medications.

SoheePlus one more line that fits our construction worker exactly: some central nervous system injuries and illnesses may also lead to depression.

RyanSo the head injury isn't background noise. It's a possible cause, and it needs a medical evaluation before anyone settles on a depressive disorder.

SoheeAnd notice the psychologist's part in this. We take a careful history, ask about injuries, illnesses and medications, and notice when the timing lines up. Then the right move in these questions is arranging a medical evaluation, and folding those results back into our own assessment.

SoheeSame principle with other conditions. On the bipolar disorder page, SAMHSA says a medical checkup can rule out other illnesses that might cause mood changes. And for attention deficit hyperactivity disorder, clinicians may use clinical testing to rule out other possible conditions.

RyanLet's pause and think. In an integrated primary care clinic, a 52-year-old woman describes 6 weeks of low mood, fatigue and slowed thinking. She also mentions several new physical complaints no doctor has looked at, and she hasn't had a physical examination in 6 years. What should the psychologist do first?

SoheeArrange a medical evaluation to rule out medical causes. New mood symptoms, new physical complaints, and no recent checkup.

RyanAnd the tempting wrong answers are worth naming. Diagnose major depressive disorder and start weekly therapy: that skips the medical check. Give a depression self-report inventory to confirm it: that measures how depressed she feels, but can't show whether an illness or a medication is behind it.

SoheeAnd reassure her that it's stress and recheck in a month: that leaves a possible physical cause unchecked. Watch for that one, because it sounds kind.

RyanA third version from our practice set: a 19-year-old college student has felt flat, tired and tearful since starting a new prescription three weeks ago, and she's never been depressed before. Same first step. The medication's possible role gets a medical evaluation before a diagnosis.

SoheeThe clue pattern across all three: new symptoms, plus something physical. An unexamined complaint, an injury, a new medication, no recent checkup.

RyanNow substances. SAMHSA explains that mental health problems and substance use disorders sometimes occur together, for three reasons.

SoheeFirst, certain substances can cause people with an addiction to experience one or more symptoms of a mental health problem. Second, some people with a mental health problem may misuse alcohol or drugs as a form of self-medication. Third, the two share some underlying causes, including changes in brain composition, genetic vulnerabilities, and early exposure to stress or trauma.

RyanAnd the overlap is common. SAMHSA says more than one in four adults living with serious mental health problems also has a substance use problem.

SoheeOpenStax adds more figures. Citing the National Institute on Drug Abuse, it says six out of 10 people who have a substance use disorder also suffer from another form of mental illness. And it reports that around 10 percent of people seeking treatment for substance use disorder have serious mental illnesses.

RyanThere's a practical obstacle too. SAMHSA notes that a substance use disorder can be hard to identify, because people can function at very different levels and often can hide their alcohol or drug use. So you have to ask, directly and without judgment.

SoheeHere's what makes diagnosis tricky. SAMHSA's own list of possible signs of a substance use disorder reads like a list of psychiatric symptoms. Sudden mood swings, irritability or angry outbursts. Periods of unusual hyperactivity, agitation, or giddiness. Appearing fearful, anxious, or paranoid, with no reason. Changes in appetite or sleep.

RyanSo paranoia in someone using methamphetamine daily might be the drug, not a separate psychotic disorder.

SoheeAnd SAMHSA lists physical signs worth integrating too, the kind of non-psychological information this knowledge statement is about: bloodshot eyes and abnormally sized pupils, sudden weight loss or gain, tremors, slurred speech or impaired coordination, and unusual smells on breath, body, or clothing.

SoheeOpenStax makes the same point when it discusses comorbidity. When people with a mental illness are also habitual drug users, it isn't always clear whether the symptoms come from the drug use, the mental illness, or both.

RyanAnd it gives a practical recommendation, citing the National Institute on Drug Abuse: observe behavior in situations where the person has stopped using drugs and is no longer in withdrawal, to make the most accurate diagnosis.

SoheeSecond pause and think. A 24-year-old man is brought to an emergency department convinced his neighbors are spying on him. His sister says he's used methamphetamine almost every day for 4 months and can't stop. He has no psychiatric history. Best first step?

RyanAssess whether the substance use is causing the symptoms before diagnosing anything else.

SoheeAnd the distractors: diagnose the disorder the symptoms most resemble and start treating it. Treat only the substance use, as if the two rarely occur together. Or assume the disorder came first and the drug use is self-medication.

RyanThat last one is clever, because self-medication is real. It's one of SAMHSA's three reasons. But assuming it skips the possibility that the drug is causing the symptoms.

SoheeHere's one more from our practice set, because it's sneaky. A graduate student has had a racing heart, panic-like anxiety and insomnia for a month. For several months, she's been taking more and more of a friend's stimulant pills every day, and she can't cut back.

RyanIt sounds like an anxiety disorder. But SAMHSA lists changes in sleep and appearing anxious with no reason among signs of substance use problems. So the first step is assessing whether the stimulant use is producing the symptoms.

SoheeAnd when both problems really are present? SAMHSA is direct: someone with a mental health problem and a substance use disorder must treat both issues.

RyanOne more connection. SAMHSA's depression page advises avoiding alcohol and recreational drugs, which can worsen symptoms and make depression harder to treat. So in our practice item about a man drinking most of a bottle of liquor every night for a year, the drinking's role gets assessed before a separate depressive disorder is diagnosed.

SoheeLet's zoom out for a second, because this is the heart of the knowledge statement. A psychological assessment that ignores medical records, medications, injuries and substance use is incomplete. The psychologist's job is to fold that information in, and to refer for a medical evaluation when something physical might explain the picture.

RyanLet's recap. Before diagnosing depression, rule out medical causes. Physical illnesses, medication side effects, and central nervous system injuries can all be involved.

SoheeA medical checkup can rule out other illnesses behind mood changes, and clinical testing can rule out other conditions that look like attention problems.

RyanSubstances can produce symptoms of mental health problems, and SAMHSA's signs of substance use, like mood swings, agitation and paranoia, overlap with psychiatric symptoms. Assess the substance's role first, ideally observing the person after use and withdrawal have ended.

SoheeWhen both a mental health problem and a substance use disorder are present, both need treatment.

RyanIf this topic feels heavy, that's understandable. These are real people with tangled stories, and you're learning to untangle them carefully. That's the work of a good psychologist.

SoheeNext time, part two: how timing and history change a diagnosis. Take a breath, and we'll see you then on EPPP Prep.

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