SSRI Dosing in OCD: Why the Depression Target Dose Falls Short
A sertraline dose that would count as an adequate depression trial left his obsessions and compulsions essentially untouched — because OCD's own dose-response curve runs well past that ceiling.
M.T., a 34-year-old man, was promoted to senior accountant four months ago and is splitting his evenings between wedding planning and a new set of client accounts. He was diagnosed with obsessive-compulsive disorder two years ago, after what he had spent most of a decade quietly reframing as ordinary carefulness — checking the stove twice became eleven times, and a five-minute handwashing routine before dinner stretched past forty. His only other medical history is intermittent tension headaches, well controlled with over-the-counter analgesics; he has never been psychiatrically hospitalized and takes no other regular medication.
His primary care physician started sertraline 50 mg eight months ago, documented as treatment for "anxiety," and raised it once, to 100 mg, over the following six weeks — the same trajectory a depression taper would follow. Nothing has meaningfully changed since. He is still washing his hands until the skin cracks, still circling back to check the front door lock from his car, and has started arriving twenty minutes late to work most mornings because of a checking ritual he cannot leave the apartment without completing. His Y-BOCS score at today's referral visit is 28, in the severe range.
The dose that would count as an adequate trial for his depression-shaped chart note and the dose his actual diagnosis requires are not the same number. Randomized trials in OCD show a dose-response relationship that continues well past the point that treats major depression — patients titrated to sertraline 200 mg or fluoxetine 60–80 mg respond at meaningfully higher rates than those held at standard antidepressant doses, a pattern MDD trials of the same drugs do not show nearly as strongly. The mechanism isn't fully settled; the leading account involves the degree and duration of serotonin transporter occupancy needed to drive the downstream changes that reduce obsessions and compulsions specifically, as distinct from the changes that lift mood. Whatever the underlying reason, the practical consequence sitting in front of the group is exactly what happened to him: a technically documented, guideline-plausible SSRI trial that never actually tested his OCD.
Setting the actual target dose
He has never had an adequate OCD trial. Six months at 100 mg with no side effects is exactly the profile of someone who tolerates the drug well and simply hasn't been given enough of it — the OCD dose-response literature is fairly consistent that meaningful separation from placebo continues up to 200 mg of sertraline, well past where a depression titration would have stopped. I'd move him to 200 mg now rather than stepping through 150 mg first; he's already proven he tolerates the drug at half that dose.
I agree with the target, not the speed. Rapid increases in SSRI dose can produce a transient jump in anxiety and agitation before the antiobsessional effect catches up, and he's already someone whose whole presentation is anxiety-driven checking. If that early activation shows up right as he's trying to trust a new medication plan, I'd rather not risk him abandoning it. A two-step increase over two weeks costs us almost nothing against a 12-week trial clock.
I'm not arguing against 200 mg as the target — only against getting there in one jump in a patient who has no dose-escalation history to reassure us with.
Then the practical plan is 150 mg for one week, 200 mg from week two onward, and the 12-week adequate-trial clock starts the day he reaches 200 mg — not the day he started sertraline eight months ago. That distinction matters for his chart: the prior six months should be documented as an underdosed trial, not a failed one, so nobody reads this case in three months and concludes SSRIs don't work for him.
Agreed: sertraline increased to 150 mg this week and 200 mg from week two, ERP referral placed today to run alongside the medication rather than after it, and a formal Y-BOCS recheck at 12 weeks from the date he reaches 200 mg.
Not agreed: whether to pre-commit, in today's note, to a further increase toward supratherapeutic dosing if 200 mg proves insufficient at 12 weeks. The clinical pharmacologist wanted that contingency documented now, arguing it saves a full additional trial-length delay later. The attending preferred to evaluate the 200 mg response on its own terms first, worried that naming the next dose today quietly turns 200 mg into a formality rather than a real endpoint the team is genuinely waiting to see the result of.