Comorbidity is the rule in psychiatric practice, not the exception. The patient with one psychiatric diagnosis often has two or three; the patient with psychiatric illness often has substantial medical comorbidity; treatment of one condition often affects others. Sequencing — what to treat first, second, third — is one of the most important treatment decisions you make.
Rank by safety first. Anything life-threatening goes to the top of the list. Acute suicidality before depression treatment. Severe alcohol withdrawal before psychiatric assessment. Acute medical instability before any psychiatric intervention. Safety overrides everything else.
Then by severity. What's causing the most functional impairment right now? What's the patient most distressed by? The severity-driven sequence often differs from what the chart would suggest based on diagnostic completeness — the patient with mild OCD and severe depression should have depression addressed first regardless of OCD's diagnostic weight.
Then by causal direction. Which condition is driving which? Sleep disorder driving mood. Substance use driving everything. Trauma driving anxiety and depression. Pain driving mood and anxiety. When a clear upstream driver exists, treating it often resolves downstream conditions partially or fully. The patient with severe OSA whose depression resolves with CPAP is a common pattern.
The common comorbidity: AUD plus depression plus anxiety. Treating depression with antidepressants while AUD continues is largely ineffective — alcohol drives mood and anxiety, and the SSRI can't out-medicate ongoing heavy drinking. Address AUD first; the downstream conditions often improve substantially as alcohol use decreases. Then layer in antidepressant and anxiety treatment if symptoms persist.
Engage the patient in the sequencing rationale. Patients often have their own priorities — and sometimes those priorities are wise (the depressed patient who wants to address their alcohol use first because they sense it's driving things) and sometimes they need reframing (the patient who wants help with insomnia but isn't ready to address the alcohol that's causing it). Shared decision-making about sequence improves engagement.
Don't try to treat everything at once. Adding multiple medications simultaneously while engaging multiple therapy modalities overwhelms patients and obscures what's working. One thing at a time, in clinical sequence, with monitoring.