Validity

• Co-morbidity

  Buckley et al (2009)- found that 50% of patients with SZ have depression or substance abuse, 29% PTSD, 23% OCD.
• Gender bias

  Longnecker et al (2010)- since the 1980s men have been diagnosed with SZ more than women.
• Culture bias

  Keith et al (1991)- found 2.1% of African Americans are diagnosed with SZ compared to 1% of the white population.
• Symptom overlap

  There is considerable overlap between

  the symptoms of SZ and other disorders.

  E.g. bipolar disorder
• Range of symptoms

  2 individuals could display very different behaviour but still be diagnosed with SZ.