Psychiatric diagnosis exists in multiple frameworks simultaneously, and sophisticated clinicians use them as complementary lenses rather than as competing systems. The DSM categorical framework dominates clinical practice; dimensional and functional frameworks add nuance that the categorical can't capture.
DSM categorical is the standard for clinical communication, billing, research definitions, and shorthand between clinicians. "Major depressive disorder, recurrent, moderate, with anxious distress" carries specific meaning across the field. The DSM categories are useful precisely because they're shared — most clinicians know what they mean, most insurance and regulatory frameworks operate on them.
Dimensional frameworks like RDoC (Research Domain Criteria) frame psychiatric problems as continuous variations on underlying neurobiological dimensions rather than discrete categories. Severity ratings. Transdiagnostic factors like rumination, avoidance, anhedonia, emotional dysregulation, sleep dysregulation. Particularly useful for severity, for research, and for understanding patients who don't fit neatly into categories.
Functional frameworks focus on what the patient can't do and what specific symptoms cause the impairment. The MDD patient can't sleep, can't enjoy hobbies, can't concentrate at work, can't engage with family. The treatment plan addresses these specific functional targets — behavioral activation for the anhedonia, sleep hygiene plus medication for the insomnia, family work for the relational withdrawal — rather than just "treating depression."
Use them deliberately for different purposes. DSM for documentation, communication, billing. Dimensional for severity tracking, research, framing patients who don't fit neatly. Functional for treatment planning — what specifically are we targeting?
Talk to patients in their preferred frame. Some patients want diagnostic clarity ("Am I depressed?"). Some want functional framing ("I can't enjoy anything anymore"). Match the conversation to the patient's framing without losing the clinical thinking behind it. The label is one tool; the functional understanding is another; the patient often responds better to one or the other depending on context.