If you have been given a recommendation for "structured outpatient" treatment, or you are weighing options against residential care, you will run into two acronyms: PHP and IOP. They are the two most common levels of structured outpatient care in the substance use system, and the difference between them is mostly a difference in intensity.
Here is what each one actually is, who it fits, and how to tell whether a program is operating at the level it claims to be.
The short version
Partial Hospitalization Program (PHP) is the higher-intensity outpatient level. Typically 20 or more hours per week of structured programming, delivered during the day, with the patient returning home (or to a sober living arrangement) at night. Maps to ASAM Level 2.5.
Intensive Outpatient Program (IOP) is the lower-intensity structured outpatient level. Typically 9 to 19 hours per week, often delivered in evening or morning sessions that allow work or school during the rest of the day. Maps to ASAM Level 2.1.
Below IOP on the ASAM continuum is Level 1 outpatient (typically 1 to 9 hours per week of individual or group therapy, sometimes paired with medication management). Above PHP is residential care (Levels 3.1, 3.5, 3.7) and medically managed inpatient (Level 4.0).
What PHP looks like in practice
A typical PHP runs 5 to 6 hours per day, 5 days per week. Programming usually includes:
- Group therapy (often the bulk of the day), including psychoeducation, CBT skills, relapse prevention, and process groups.
- Individual therapy (typically 1 to 3 times per week).
- Medication management with a prescriber, integrated into the program.
- Family sessions or family programming as appropriate.
- Case management for housing, work, legal, and other social issues.
- Medical monitoring for patients early in abstinence or on stabilizing medications.
PHP is sometimes called "day treatment" or "day hospital" in older terminology. The patient is in programming during business hours and goes home at the end of the day.
What IOP looks like in practice
A typical IOP runs 3 to 4 hours per session, 3 days per week. Programming is compressed:
- Group therapy, typically 2 to 3 hours per session, structured around CBT, relapse prevention, or similar evidence-based curricula.
- Individual therapy, often weekly.
- Medication management, usually on a separate schedule.
- Family work, often as an add-on rather than embedded in the weekly schedule.
IOP is designed to accommodate a working adult or a student. Many IOPs offer evening tracks (typical: 6 to 9 p.m., three evenings a week) specifically to preserve the rest of life. Telehealth IOP has become widespread since 2020 and is now a common option.
Who PHP fits
PHP is appropriate for patients who need significantly more structure than IOP can provide, but do not require 24-hour care. Common indications:
- Early post-detox, when physical stabilization has been achieved but relapse risk remains high.
- Step-down from residential treatment, as a transitional level of care.
- Initial treatment for patients with severe substance use disorders who are safe at home but not stable enough for a working schedule.
- Co-occurring mental health concerns that require close clinical contact.
PHP is not appropriate for patients whose living environment is actively unsafe (ongoing violence, active substance use by others in the home in ways the patient cannot avoid), those situations require a higher level of care or, at minimum, housing stabilization before PHP can be effective.
Who IOP fits
IOP is appropriate for patients who:
- Have achieved initial stabilization and are working on skills acquisition and relapse prevention.
- Need to maintain work, school, or caregiving responsibilities during treatment.
- Are stepping down from PHP or residential.
- Are in the early phase of moderate substance use disorder where structured but flexible care is clinically sufficient.
The ASAM Criteria are explicit that the level of care should match the patient's clinical needs, not the patient's preference for minimal disruption, and not the program's preference for maximum billing. Many patients are appropriately placed in IOP from the start, without needing PHP or residential care first.
What neither level does alone
Both PHP and IOP are delivery structures; the clinical content is what determines outcomes. A few things the evidence supports across both levels:
- Medications. For patients with opioid use disorder or alcohol use disorder, MOUD or MAUD should be integrated into the program. See Medications for Opioid Use Disorder and Medications for Alcohol Use Disorder. A program that does not offer or coordinate medication is operating below the standard of care for these disorders.
- Evidence-based therapy curricula. CBT for SUD, motivational interviewing, and contingency management (where available) are the standard. A program that describes its approach as generic "talk therapy" or primarily "12-step programming" is not working from the current evidence base.
- Family involvement. CRAFT, BCT, or other family approaches have strong evidence. Programs that exclude family contact entirely, or that limit family involvement to "family weekend" theater, are leaving outcomes on the table.
- Co-occurring treatment. Most patients with substance use disorders have co-occurring mental health conditions. Programs that treat substance use in isolation from depression, anxiety, PTSD, or ADHD are ignoring a major predictor of outcome.
How to tell the difference in a program you are evaluating
A few specific questions that separate well-run programs from the rest:
- How many hours per week, across how many days? PHP: 20+ hours, 5 days. IOP: 9 to 19 hours, 3 days. Programs that blur the boundary between PHP and IOP are sometimes up-coding or down-coding for billing.
- What is the clinical curriculum? Ask for the topics covered across a typical week. The answer should reference CBT, MI, relapse prevention, or similar. "We focus on what each individual needs" is not an answer; that is a deflection.
- Do you offer MOUD/MAUD, or do you partner with prescribers who do? This should be a straightforward yes, with a clear answer about how medications are integrated.
- What is the average length of stay, and what are the criteria for step-up or step-down? Good programs have clinical pathways, not fixed timelines.
- Who are the clinicians, and what are their credentials? LPC, LCSW, LMHC, LCADC, and prescribing clinicians (MD, DO, NP, PA) should be identifiable. Programs that respond vaguely ("we have a team of counselors") may not have licensed clinical staff.
More detailed questions are in Questions to Ask a Program Before You Enroll.
The bottom line
PHP is higher-intensity structured outpatient care (20+ hours/week, 5 days). IOP is lower-intensity structured outpatient care (9 to 19 hours/week, 3 days). The level that fits depends on clinical assessment, not on what the program wants to sell or what the family thinks should be the "serious" option. For most people with substance use disorders, structured outpatient care, PHP or IOP, is the level where the most durable work happens. Residential is a starting point for a specific subset of patients. Outpatient is where most of recovery actually lives.
What to read next
What to read next
Most people with substance use disorders can be treated effectively without residential rehab. Outpatient care, medications, and harm reduction are real options backed by clinical evidence. You do not have to make a permanent decision today. The next step can be small.