As these examples demonstrate, although provisions for prisoners who are held in solitary confinement regimes vary between States, such regimes typically involve further restrictions and security measures in addition to the physical segregation of prisoners from the general prison population. It is difficult to see what legitimate penal purpose is served by restricting prisoners’ access to craft and hobby materials and other in-cell activities, or subjecting them to routine strip searches even when the prisoner had no physical contact with others, and how such practices are conducive to rehabilitation and reintegration purposes or, indeed, to prison security. Such regimes are contrary to international standards and good practice and, in some cases, can be in violation of international law. Moreover, they result in boredom and frustration which may in turn lead to mental health and behavioural problems. 4.3 R  esearch findings and recommendations regarding prison design and environmental factors There are few studies of the relationship between the prison environment and prisoner behaviour in general, and no studies which focus on segregation units. The sparse literature and few empirical studies reaffirm the fairly obvious: “the design of the prison environment is crucial to its operation and to the impact it has on the achievement of correctional goals for inmates, staff and public users” (Fairweather, 2000:47).. Environmental conditions in prison also affect prisoners’ health and can “easily exacerbate the symptoms of mental illness for some people. In fact, the prison environment itself can contribute to increased suicide and the inability of inmates with serious mental illness to adjust. Environmental factors can also elicit significant adjustment reactions from inmates who may not have had a previous diagnosis but who become ill while incarcerated” (Hills at al. 2004:15). Further, design and environmental factors can influence the frequency and severity of violent incidents60. The design of a prison is closely linked to its regime, as the layout of the prison dictates, to a large degree, the activities and human interaction that can take place within it. Studies of the effects of specific prison design features on prisoners and staff indicate that these can have ‘negative’ or ‘positive’ effects. Positive design features are those that reduce the institutionalised atmosphere in prisons, lessen stress, aggression and violence, and generally increase prisoners’ wellbeing. Negative features are those that foster and increase the above. Some of the design features that are cited as positively influencing behaviour and wellbeing are those which: Increase opportunities for social interaction between prisoners and between prisoners and staff Clearly, segregation units are not designed for continuous prisoner association. Yet, even in units or prisons designed for solitary confinement the design should allow for some degree of social interaction. This can be done through the inclusion of communal areas for recreational, sports and games facilities and so on. Sourcebook on solitary confinement: Design, physical conditions and regime in solitary confinement units 49