A Stepwise Approach to Differential Diagnosis
A good interviewer should consider as many diagnoses as possible while investigating the nature of a person’s distress (Feinstein 1967). Although an entire manual (First 2014) has been designed specifically to teach the differential diagnosis for DSM-5 (American Psychiatric Association 2013), we provide in this chapter a general six-step approach to generating the differential diagnosis in older adults. As you develop your clinical decision-making skills, it will be helpful to follow these steps sequentially so you will consider each possible cause of mental distress.
Step 1: Consider to What Extent the Signs and Symptoms Are Related to a Stressor or Functional Change
Your thorough evaluation of an older adult should eventually include recommended health screening and some kind of functional assessment. Although formal assessments of physical health and functional ability are beyond the scope of this book, you should be aware of how normal aging affects balance, cognition, memory, smell, sleep, and vision. Remember that there can be significant differences between a patient’s chronological age and her functional age. Function also depends on baseline ability, and a thorough social history imparts a sense of how a patient’s current behavior relates to her usual behavior. Even in a brief interview, it is useful to observe how your patient communicates and behaves and to compare her communication and behavior with those appropriate for her age, culture, and education. If you observe a disjunction, consider these possibilities:
- The patient is having a transient response to a particular event. If distress or impairment develops as a maladaptive response to an identifiable psychosocial stressor, consider an adjustment disorder.
- The patient has an immature defense mechanism, which may indicate a personality trait or disorder.
- The patient is having a developmental conflict in a particular relationship.
- The patient is experiencing a change in functional ability.
Step 2: Consider to What Extent the Signs and Symptoms Are Related to a Caregiver Conflict
As human beings we are, in the words of the philosopher Alasdair MacIntyre (2012), “dependent rational animals” because we depend on “particular others for protection and sustenance” (p. 1). For older adults, aging can be experienced as a return to dependence after decades of perceived independence. Older adults depend on other people as caregivers. As you evaluate your patient, observe how she does (or does not) speak about her caregivers. 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.
- A caregiver is experiencing mental distress, which results in the caregiver unintentionally worsening a patient’s signs or symptoms.