Six Steps to Better DSM-5 Differential Diagnosis

ORLANDO—Patients often come for treatment with the presenting symptom of depression, but the path from symptom to diagnosis is not as straightforward as it may appear. Many DSM disorders could explain the symptom of depression. 

“Your job as a clinician is to figure out what is the right [disorder] so that you can start the right treatment,” said Michael B. First, MD, Professor of Clinical Psychiatry at Columbia University, New York in his presentation at the 27th Annual U.S. Psychiatric and Mental Health Congress. 

“Most patients do not come into our offices saying ‘I have major depressive disorder, give me duloxetine,’” said Dr. First, who is the author of DSM-5 Handbook of Differential Diagnosis. “[Differential diagnosis] is the bread and butter of our task as clinicians.” 

Patients come into the office seeking relief from broad symptoms such as depressed mood or fatigue, and clinicians must consider which of all the disorders in DSM could account for those symptoms. 

Step 1: Rule Out Malingering and Factitious Disorder

Dr. First breaks the diagnostic process into six steps, starting with ruling out malingering or factitious disorder. This is essential because “our work depends on good faith collaborative effort between clinician and patients,” he said. “If the patient is not being honest with report of symptoms, it is impossible to make an accurate diagnosis based on symptoms.” 

Malingering disorder differs from factitious disorder based on motivation. Malingering is driven by achievement of clearly recognizable goals, such as insurance compensation or avoiding responsibilities, and is not a mental disorder, while factitious disorder occurs in the absence of obvious external award. A person with factitious disorder wishes to take on the role of sickness for psychological reasons. 

However, Dr. First cautions against treating patients like a hostile witness in a courtroom. Suspicion of these disorders should only be raised in certain settings and situations. 

Step 2: Rule Out Substance Etiology 

Next, clinicians should consider whether the patient’s’ symptoms might be due to substance abuse. “Virtually any psychiatric presentation can be caused substance use,” said Dr. First.

 To make this determination, clinicians can interview the patients, check with the patient’s family members, look for signs of substance use such as active intoxication, and order laboratory tests that screen for recent use. Medication side effects should also be considered, Dr. First noted. 

 If signs of substance abuse are evident, the etiological relationship between substance and psychiatric symptoms must be considered. Psychiatric symptoms might result from the direct effect of the substance on the CNS, substance use could be a consequence or feature of a primary psychiatric disorder, or substance use and psychiatric symptoms might be completely independent and truly comorbid. 

 “Even if independent, it’s well known that psychiatric symptoms and substances can make each other worse,” said Dr. First. 

 Step 3: Rule Out Disorder Due to a General Medical Condition

Clinicians should consider direct medical examination for conditions that commonly account for psychiatric symptoms, such as depression resulting from thyroid dysfunction.

 “The treatment implications here are potentially profound,” said Dr. First. 

If a general medical condition (GMC) may be responsible for psychiatric symptoms, clinicians encounter several possible etiological relationships. Medication may be responsible for psychiatric symptoms, the psychiatric symptoms might cause or adversely affect the GMC, or the symptoms and GMC may be coincidental. 

In addition, the GMC might cause mental health symptoms through a direct physiological effect on the brain, such as through having a stroke, or through a psychological mechanism, commonly seen when patients experience depressive symptoms in response to cancer diagnosis. In the case of depression caused by cancer diagnosis, the patients would be diagnosed with major depressive disorder or adjustment disorder. 

 For clues to determining whether a GMC is a factor, clinicians can assess temporal relationship, such as if the psychiatric symptoms began following the onset of the GMC, if they vary in severity with the severity of the GMC, and if they remit when the GMC resolves. 

 An atypical symptom pattern, age of onset, or course also may warrant a  medical workup. For example, first onset of manic episode in an elderly patient “is a huge red flag,” said Dr. First, as is a person who has a mild depression accompanied by severe memory or weight loss. 

 Step 4: Determining the Specific Primary Disorder

At this point in the process, the clinician should pinpoint the specific primary disorder.

 “Many diagnostic groupings in DSM-5 are organized around common presenting symptoms,” explained Dr. First. He added that decision trees in his book can provide guidance on choosing among the primary disorders and that differential diagnosis table can help ensure other likely candidates explaining the patient’s behavior have been considered and ruled out. 

 Step 5: Differentiate Adjustment Disorders From Residual Other or Unspecified Categories

If patients present with subthreshold symptoms that are still severe enough to cause clinically significant distress or impairment, clinicians need to think about using Adjustment Disorder versus using Other Specified/Unspecified Disorder.

 “If symptoms are a maladaptive response to a psychosocial stressor, then use Adjustment Disorder,” said Dr. First. “Otherwise, we give the appropriate residual category.” 

 For example, a clinician might use Other Specified to give the reason for not meeting criteria or use Unspecified to choose to withhold indication of the reason or if the reason is unknown.

Step 6: Establish Boundary With No Mental Disorder

 Finally, clinicians should evaluate whether the patient’s symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning. 

 “This begs the question of what it means to be clinically significant. And that’s a judgment call. Usually if someone comes to you for help that’s a sign it could be clinically significant, or the problem could have been picked up in a primary care setting,” said Dr. First. 

He added that the symptoms also must represent an internal biological or psychological dysfunction in the patient. For example, a patient mourning the loss of a close family member may experience uncomplicated bereavement, which causes a great deal of distress but would not qualify as a mental disorder because the distress is not a psychological dysfunction. 

 —Lauren LeBano 

 Reference

 1. First MB. [Psych Congress conference presentation]. September 19, 2014. DSM-5: a practical overview of changes.