An estimated 84,000 incarcerated individuals face solitary confinement in the United States criminal justice system. Solitary confinement is seen as a cruel punishment, with lasting effects, for incarcerated individuals. Human rights organisations, medical associations, policymakers, and incarcerated people have argued for the discontinuation of solitary confinement. After being in solitary confinement for an extended period, incarcerated people can suffer worsening and future mental health issues, physical health concerns and issues with relationships during and after serving their time in prison. This article reviews the available research and the purpose of the article is to show the detrimental effects solitary confinement has on incarcerated individuals. Clinical and policy implications for prisons that use solitary confinement are discussed to dissuade usage.