Solitary confinement is a punishment used in prison systems where inmates are isolated from the general population and have little contact with others. It is used both to protect inmates and as punishment for breaking rules. However, long term solitary confinement of over 20 hours per day for years has psychological effects and is considered inhumane by some. There are two types - disciplinary for short periods as punishment and administrative for indefinite periods for high risk inmates. Administrative solitary can last months or years and has been found to cause mental and physical harm, especially for those with preexisting conditions.