Sometimes known as obsessive thoughts or ruminations, obsessions are unwanted and recurrent thoughts, doubts, or images that intrude into one's mind despite attempts to resist or control them. They may be fleeting thoughts, or they may stick in one's mind for long periods of time despite attempts to dislodge them. They are upsetting and may cause anxiety, guilt and shame. They usually lead to compulsions and/or avoidance (see above) as people try to remove or control the thoughts, deal with the situations that the thoughts refer to, or reduce the distress. The thoughts may be about almost any content, but common themes include dirt and contamination and their effects on self or others, harm that one may cause to others or failure to prevent harm from occurring, personally unacceptable blasphemous, immoral, or sexual thoughts, or excessive preoccupation with moral, religious or existential questions.