Background <p>Intensive Home Treatment (IHT) is an acute intensive outpatient treatment intended to replace or shorten clinical admission for patients in psychiatric crisis. Recent studies have demonstrated that IHT is noninferior to clinical admission in several patient groups. However, it remains unclear which patient characteristics, if any, predict the degree of reduction in crisis severity after IHT. Furthermore, the effectiveness of IHT in reducing crisis severity when used to shorten clinical admissions remains unclear.</p> Aims <p>To elucidate what variables predict the course of crisis severity in IHT.</p> Method <p>We conducted an exploratory prospective naturalistic study. We recruited 120 participants referred for IHT. A list of putative predicting variables was constructed on the basis of interviews with IHT staff and a patient and support system council. To measure crisis severity, symptom severity questionnaires (SQ-48; symptom questionnaire 48) were administered at the beginning and after 3 and 6 weeks of IHT.</p> Results <p>None of the putative predicting variables predicted the course of crisis severity during IHT. Crisis severity decreased, the mean SQ-48 decreased from 84 to 46 (Cohen’s d 1.25, 95% CI 0.66–1.81). Participants with bipolar or psychotic disorders reported less severe baseline symptoms but improved equally to other participants. In participants receiving IHT after admission, no clear improvement was observed.</p> Conclusions <p>Crisis severity decreased during IHT, but baseline participant characteristics did not predict outcome of IHT. The lower baseline crisis severity in participants with bipolar or psychotic disorder suggests that clinicians have a different referral pattern to IHT for patients with these diagnoses. IHT did not further improve crisis severity if initiated after clinical admission. This suggests that both the need for IHT as aftercare and its timing should be critically evaluated by clinicians.</p>