Critical time intervention reduces psychiatric rehospitalisation in homeless people

Homeless man

Recent work by Suzanne Fitzpatrick and colleagues from Heriot Watt University has investigated the experiences of people who are affected by what they call multiple exclusion homelessness; a combination of homelessness, substance misuse, ‘street’ activities such as begging and street drinking, and institutional care (e.g. prison).

Their quantitative survey shows that there is considerable overlap between homelessness and these other forms of social exclusion (substance misuse, street culture etc), which clearly makes caring for this population a complex challenge (Fitzpatrick, 2012).

One approach to caring for homeless people with many other complex issues (including mental illness) is Critical Time Intervention, which was originally developed by researchers and clinicians at Columbia University and New York State Psychiatric Institute.

Critical Time Intervention (CTI) is:

An empirically supported, time-limited case management model designed to prevent homelessness and other adverse outcomes in people with mental illness following discharge from hospitals, shelters, prisons and other institutions.

The theory behind the intervention is that homelessness and other adverse events can be minimised or prevented by:

  • Strengthening the individual’s long-term ties to services, family, and friends
  • Providing emotional and practical support during the critical time of transition

Post-discharge care is provided by a social worker who has already established a relationship with the patient during their institutional stay (in psychiatric hospital).

A new randomised controlled trial published in Psychiatric Services explores the impact of critical time intervention on the occurrence of rehospitalisation among formerly homeless individuals with severe and persistent mental illness.


150 previously homeless people, currently residing in a New York City psychiatric hospital (and planning to stay in the same city on discharge) were included in the study. They were mostly male (71%) and African-American (62%) and aged 37.5 years on average. Many had a diagnosis of psychosis (61% lifetime diagnosis of schizophrenia and 35% schizoaffective disorder) and almost all (90%) had issues with substance misuse or dependence.

Patients were randomised to one of two groups:

  1. Usual care (various community based services)
  2. Usual care plus Critical Time Intervention (CTI)

Randomisation was single blind (the researchers who assessed the data were blind to the group into which patients had been randomised) and it was unclear from the study how allocation to treatment was carried out.

CTI was delivered by a trained social worker who got to know the patient during their stay in hospital and saw them regularly for 9 months post-discharge. Patients were followed up at 6-week intervals for a total of 18 months.


  • Returning to psychiatric hospital was less frequent in the CTI group at all but one 6-week follow-up
  • The treatment groups spent significantly different numbers of nights in psychiatric hospital during the last 18 weeks of the study:
    • 1,183 nights in the CTI group
    • 1,508 nights in the usual care group
  • Compared to usual care, CTI significantly reduced the risk of psychiatric rehospitalisation in this period:
    • 18% with CTI
    • 27% with usual care
    • (adjusted OR 0.11, 95% CI 0.01 to 0.96)
  • The author investigated a number of covariates (these are variables that possibly predict the outcome) and found that housing stability was associated with a reduced likelihood of rehospitalisation (OR 0.96, 95% CI 0.92 to 0.99)


The authors concluded:

This study demonstrated that Critical Time Intervention, primarily designed to prevent recurrent homelessness, also reduced the occurrence of rehospitalisation after discharge.

Future studies will need to investigate whether CTI can also help reduce further psychiatric hospital stays in non-homeless people with severe mental illness.

For the time being, mental health and social care professionals should consider CTI as a relatively inexpensive intervention that they can add on to their existing services for homeless people with complex needs.


Tomita A, Herman DB. The impact of critical time intervention in reducing psychiatric rehospitalization after hospital discharge. Psychiatr Serv. 2012 Sep 1;63(9):935-7. doi: 10.1176/ [PubMed abstract]

Fitzpatrick S, Bramley G, Johnsen S. Multiple Exclusion Homelessness in the UK: an overview of key findings, briefing paper no. 1 (PDF). Institute for Housing, Urban & Real Estate Research, School of the Built Environment, Heriot-Watt University, 2012.

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Andre Tomlin

André Tomlin is an Information Scientist with 20 years experience working in evidence-based healthcare. He's worked in the NHS, for Oxford University and since 2002 as Managing Director of Minervation Ltd, a consultancy company who do clever digital stuff for charities, universities and the public sector. Most recently André has been the driving force behind the Mental Elf and the National Elf Service; an innovative digital platform that helps professionals keep up to date with simple, clear and engaging summaries of evidence-based research. André is a Trustee at the Centre for Mental Health and an Honorary Research Fellow at University College London Division of Psychiatry. He lives in Bristol, surrounded by dogs, elflings and lots of woodland!

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