PHP and IOP are both outpatient levels of care. Neither includes an overnight stay in the treatment program.
The main difference is intensity. A partial hospitalization program—often called PHP—usually provides more structure and clinical contact than an intensive outpatient program, or IOP. ASAM’s Fourth Edition uses high-intensity outpatient for Level 2.5, although PHP remains common public and insurance language.
The exact schedule is not universal. State requirements, payer rules, clinical population, and program design all matter.
PHP vs. IOP at a glance
| Feature | PHP / high-intensity outpatient | IOP |
|---|---|---|
| Overnight stay | No | No |
| Relative intensity | Higher | Lower than PHP; higher than standard outpatient care |
| Schedule | Often most weekdays for substantial blocks of time | Often several sessions across multiple days each week |
| Medical stability | Usually requires ability to remain outside hospital care overnight | Usually requires enough stability for fewer program hours |
| Home environment | Must be safe enough outside program hours; separate recovery housing may be considered | Stable support and transportation may be especially important |
| Common transition role | Step down from inpatient/residential or step up from IOP | Step down from PHP/residential or step up from standard outpatient care |
This table describes relative differences, not guaranteed hours or services.
What PHP may include
PHP may include group therapy, individual sessions, addiction medicine, psychiatric care, medication management, nursing services, case management, drug testing, family sessions, and discharge planning.
Because the person leaves after programming, PHP is not a substitute for hospitalization when 24-hour medical or psychiatric management is needed.
What IOP may include
IOP often uses many of the same clinical tools with fewer weekly program hours. It can provide enough structure to address substance use while leaving more time for work, school, caregiving, medical appointments, and practice in the home environment.
That flexibility has a limit. If use continues, withdrawal risk emerges, psychiatric symptoms destabilize, or the home setting becomes unsafe, the treatment team may recommend stepping up.
Housing is separate from clinical care
PHP and IOP do not provide overnight treatment beds. A person may live at home or in a recovery residence, but housing and clinical treatment are distinct services. Ask whether housing is owned, operated, referred, or financially connected to the provider. Also ask what happens to housing if treatment coverage changes.
How placement is decided
A clinician may consider withdrawal risk, medical conditions, psychiatric symptoms, recent use, ability to participate, transportation, medications, prior response to care, and the recovery environment.
The most intensive available option is not automatically the best option. The goal is a setting that is safe, sufficient, and no more restrictive than necessary across the full range of levels of care.
Questions to ask
- How many clinical hours are scheduled for this specific program?
- Which services are included, and which are billed separately?
- Is addiction medicine or psychiatry available onsite?
- How are medications continued without interruption?
- What support is available after program hours?
- Is housing separate from treatment?
- What would cause a step up or step down?
- What is the plan if transportation or caregiving disrupts attendance?
- How are co-occurring mental health needs treated?
Next step
Ask each provider for its actual weekly schedule, staffing, services, after-hours plan, and housing arrangement. Compare the real programs, not only the labels. Our guide to how to choose an addiction treatment program lists what to verify, and what happens after rehab covers the continuing-care plan that should follow either level.
Sources
- ASAM, The ASAM Criteria
- ASAM, Criteria FAQ
- National Institute on Drug Abuse, Principles of Drug Addiction Treatment
Medical disclaimer: General education only. A licensed clinician should assess the appropriate level of care. Call 911 for immediate danger or a medical emergency; call or text 988 in the United States for a mental health or suicide crisis.
Frequently asked questions
Is PHP inpatient treatment?
No. Despite the traditional name “partial hospitalization,” PHP is outpatient care and does not include an overnight hospital stay.
Can someone work during PHP or IOP?
Some IOP schedules are compatible with work. PHP often occupies much of the day. Actual feasibility depends on program hours, transportation, symptoms, and job demands.
Can a person move from IOP to PHP?
Yes. Treatment can step up when needs intensify and step down when a lower level can safely provide the necessary care.