Neuropsychological and Cognitive Performance of Homeless Adults Graham Pluck and Kwang–Hyuk Lee University of Sheffield Rajan David Sheffield Care Trust, Sheffield, United Kingdom Sean A. Spence and Randolph W. Parks University of Sheffield Many homeless people may have been exposed to events and situations that could potentially produce neuropsychological impairments. In the current study, 80 homeless participants underwent a battery of tests designed to 1) estimate long-standing established memory and intelligence, which was assumed to indicate prehomeless function and 2) measure current memory and intelligence function. Mental health screening and substance misuse data were also obtained. Results indicated that current memory and IQ were significantly lower than the estimated normal population means and also their prehomeless estimates. The memory score change was from 100.5 to 90.3 ( p  .001) and IQ change from 98.8 to 95.6 ( p = .038). The interaction between task type (memory or IQ) and measure (prehomeless or current) was also significant ( p = .003), signifying that there was a greater change in the domain of memory function than in IQ. Many participants reported substance misuse and clinically significant mental health concerns. We conclude that the homeless individuals in our sample appear to have suffered a reduction in cognitive function, which may have occurred either during homelessness or prior to it. Keywords: cognition, homelessness, intelligence, IQ, memory, premorbid Homelessness presents a range of challenges to those govern- mental and nongovernmental agencies that occasionally or rou- tinely deal with vulnerable and insecurely housed individuals. These include health services, social care providers, governmental benefit agencies, and charities. It has been estimated that within the European Union around 2.7 million people can be defined as homeless (i.e., either literally roofless, in inappropriate housing, or living in overcrowded conditions; Avramov, 1999). When the definition of homelessness is limited to those who are literally roofless, living in temporary shelters or squats, it has been esti- mated that there are around 85,000 homeless individuals in the United Kingdom (U.K.; Kenway & Palmer, 2003), with compa- rable figures of 35,000 in Canada and 350,000 in the United States. (Murphy, 2000). Indeed, homelessness has emerged as a major social concern in most developed countries (Toro, 2007). There are multiple societal and economic factors that influence the level of homelessness, including access to affordable housing, national stability, societal wealth, and local welfare provision (Berger & Tremblay, 1999). However, there are also likely to be multiple intrapersonal factors. Homeless individuals tend to dis- play personality profiles characterised by pessimism and a nega- tive perspective on the past (Pluck et al., 2008) and to report high levels of traumatic events in their childhoods (Pluck et al., 2011; Spence et al., 2006). It is, perhaps then, not surprising that many homeless people display complex psychosocial problems that ap- pear to predate their homelessness and often remain after rehous- ing (Vostanis, Grattan, & Cumella, 1998). In addition, systematic literature reviews of cognitive function in children and adolescents (Parks, Stevens, & Spence, 2007) and adults (Backer & Howard, 2007; Burra, Stergiopoulos, & Rourke, 2009; Spence, Stevens, & Parks, 2004) have described high levels of cognitive impairment in samples of homeless individuals. Many homeless people may be at the lower range of cognitive abilities and this may have contributed to their difficulties within society. This could be due to childhood socioeconomic disadvantage, poor family functioning, and inadequate access to education. For exam- ple, a homeless sample in the United States was found to have notably poor reading ability (Solliday–McRoy, Campbell, Melchert, Young, & Cisler, 2004). In another study of neuropsy- chological test performance in homeless individuals in the United States, it was found that education level was the only statistically significant demographic factor, accounting for 29% of the variance (Gonzalez, Dieter, Natale, & Tanner, 2001). Alternatively, it is feasible that many homeless people have suffered a decline in cognitive function as a consequence of homelessness. In support of this suggestion, homelessness is as- sociated with a range of factors with the potential to impair cognition, including poor nutrition (Evans, 1996), raised levels of substance misuse (Pluck, Lee, & Parks, 2007), and mental illness Graham Pluck, Kwang–Hyuk Lee, Sean A. Spence, and Randolph W. Parks, Academic Clinical Psychiatry, University of Sheffield, Sheffield, United Kingdom; Rajan David, Homeless Assessment and Support Team, Sheffield Care Trust, Sheffield, United Kingdom. Randolph W. Parks is now at the Choate Mental Health Center, Illinois Depatement of Human Services, in Anna, Illinois, USA. We regret the death of Sean A. Spence during the final stages of this project. This research was supported by a grant from the Sheffield Health and Social Research Consortium. We thank David Coldwell for being a homeless-service user consultant to the project. Correspondence concerning this article should be addressed to Dr. Graham Pluck, Academic Clinical Psychiatry, University of Sheffield, The Longley Centre, Norwood Grange Drive S5 7JT, United Kingdom. E-mail: g.pluck@sheffield.ac.uk Canadian Journal of Behavioural Science © 2011 Canadian Psychological Association 2011, Vol. ●●, No. ●, 000–000 0008-400X/11/$12.00 DOI: 10.1037/a0025382 1