Although diagnoses are the known result of an interview, a good interviewer should generate more hypotheses than diagnoses because an interviewer is investigating the nature of a person’s distress (Feinstein 1967). In these investigations, the set of possibilities is large. Although an entire manual has been designed specifically to teach the differential diagnosis for DSM-5 (First 2014), it is helpful to review the following general seven-step approach to generating the differential diagnosis in children and adolescents. As you develop your clinical decision making, it is helpful to follow these steps sequentially so that you will consider each possible cause of mental distress.
Always consider if a patient is intentionally producing findings, because an honest report of psychiatric symptoms and signs is the true foundation for developing a diagnosis and treatment plan. An honest report strengthens the therapeutic alliance, whereas a dishonest report weakens the therapeutic alliance.
If intentionally produced findings are associated with an obvious external award—such as time off from school or work or change in caregivers—consider the possibility of malingering. Remember that malingering can be concomitant with other medical and psychiatric diagnoses.
If intentionally produced findings are associated with the desire to be perceived as ill or impaired, consider factitious disorder.
A patient can also unconsciously produce signs or symptoms to resolve a conflict, to validate his inability to function, or to attempt to secure assistance. In these situations, consider one of the somatic symptom and related disorders.
If you are thoroughly evaluating a young child, your evaluation should eventually include formal developmental assessment, a skill beyond the scope of this book. Even when you are interviewing older children, adolescents, and adults, however, you should consider a patient’s developmental stage, which can be quite different from the developmental stage you would expect based on his age, background, and education (summarized in Chapter 12, “Developmental Milestones”). A thorough social history also will give you a sense of how a patient’s current behavior relates to his usual behavior. Even in a brief interview, it is useful to observe how your patient communicates and behaves and compare his communication and behavior with those appropriate for his age, culture, and education. If you observe a disjunction, consider these possibilities:
• The patient is experiencing a transient regression in response to a particular event.
• The patient is using an immature defense mechanism, which may indicate a personality trait or disorder.
• The patient is experiencing a developmental conflict in a particular relationship.
• The patient has a developmental delay or intellectual impairment.
Human beings are, in the words of the philosopher Alasdair MacIntyre, “dependent rational animals” because we depend on “particular others for protection and sustenance” (MacIntyre 2012, p. 1). This dependence is acute for children and adolescents. By degrees of ability, age, development, impairment, and temperament, children and adolescents depend on both adults and fellow children as caregivers. Caregivers can aid or injure a child or an adolescent. As you 191evaluate a child or an adolescent, observe how he does (or does not) speak about the caregivers in his life, either directly or through transitional objects. As you observe, consider these possibilities:
• A caregiver and the patient have communication difficulties or cultural differences.
• A caregiver is a poor fit with the patient.
• A caregiver is abusing, neglecting, or otherwise harming the patient.
The variety of substances that people use and misuse is remarkable, as are the clinical effects of substance use. People can experience mental distress during substance use, intoxication, and withdrawal. When you seek the cause of a patient’s distress, always consider drugs of abuse, as well as prescription, over-the-counter, and herbal medicines. Ask about substances ingested both intentionally and unintentionally. People often underreport their use of substances, so consider these possibilities:
• Substances directly cause the patient’s psychiatric signs and symptoms, a substance/medication-induced mental disorder.
• A patient uses substances because of a mental disorder and its sequelae.
• A patient uses substances and experiences psychiatric signs and symptoms, but the substance use and signs and symptoms are unrelated.
A patient can present with another medical condition that mimics psychiatric signs and symptoms. Sometimes, his presentation with these findings is a sentinel event that occurs in 192advance of the other stigmata of a medical condition. Alternatively, he may develop psychiatric signs and symptoms years after his presentation for another medical condition. Clues that another medical condition may be related to a mental disorder include an atypical presentation, abnormal age at onset, and abnormal course. Consider these possibilities:
• Another medical condition directly alters the patient’s psychiatric signs and symptoms.
• Another medical condition indirectly alters the patient’s psychiatric signs and symptoms, as through a psychological mechanism.
• The treatment for another medical condition directly alters the patient’s psychiatric signs and symptoms.
• The patient’s mental disorder, or its treatment, causes or exacerbates another medical condition.
• The patient has a mental disorder and another medical condition, but they are causally unrelated.
“Normality” covers a wide range of behaviors and thoughts that vary across cultural groups and developmental stages. In DSM-5, a mental disorder causes a “clinically significant disturbance in an individual’s cognition, emotional regulation, or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning” (American Psychiatric Association 2013, p. 20). Diagnoses are summaries of information that allow you to categorize the experiences of a distressed person in a way that generates useful information about prognosis, preferred treatment strategies, and expected outcomes. DSM-5 seeks parsimony, but diagnoses are not mutually exclusive, so consider these possibilities:
• Condition A predisposes a patient to Condition B, or vice versa.
• An underlying condition, such as a genetic predisposition, predisposes a patient to both Conditions A and B.
193• A mediating factor, such as alterations in reward systems, influences a patient’s susceptibility to both Conditions A and B.
• Conditions A and B may be part of a more complex and unified syndrome that has been artificially split in the diagnostic system.
• The relation between Conditions A and B is artificially enhanced by overlaps in the diagnostic criteria.
• The comorbidity between Conditions A and B is coincidental.
When a patient’s symptoms and presentation do not fulfill the criteria for a specific mental disorder but cause clinically significant distress or impairment, consider alternatives. If the distress or impairment has developed as a maladaptive response to an identifiable psychosocial stressor, consider an adjustment disorder. If the patient’s symptoms are not secondary to a stressor, consider an other specified diagnosis (when you are specifying why a patient’s experience does not meet the criteria for a specific diagnosis) or an unspecified diagnosis (when you do not specify why a patient’s experience does not meet the criteria for a specific diagnosis) or the possibility of no psychiatric diagnosis at all. After all, the boundaries between normality and abnormality are ultimately determined through the exercise of experienced judgment.194