(This post gives the example of schizophrenia from some A-level courses. IB Diploma students should use depression instead.)
Cultural bias is highly relevant in the content area of psychopathology (abnormal psychology), especially in the definition of abnormality as ‘deviation from social norms.’ This creates the question of whose social norms? Behaviours that may seem normal in one culture are sometimes viewed as extremely abnormal in another. Behaviour being defined as abnormal is the initial step of diagnosis of a mental disorder, which is why cross-cultural diagnosis is controversial. When the medical professional is from one culture and the patient from another, there is the potential for cultural bias.
Schizophrenia and cultural bias
The behaviour that results in a diagnosis of schizophrenia is an example of deviation from social norms in many cultures. There is reduced social functioning and sometimes auditory hallucinations and delusions of grandeur or persecution, as well as reduction in speech and an inability to hold a consistent conversation.
However, with regards to one of the main symptoms, in Maori culture matakites are visionaries (prophets) who hear voices and they are highly respected in the community. The voices are not regarded as auditory hallucinations and the matakites are not diagnosed with schizophrenia (Lakeman 2001).

Wai Turoa Morgan is a Maori Matakite. She is seen as the ‘grandmother’ of the shamans. The Maori possess great knowledge about the power of ancestors and their wisdom. A matakite hearing voices is seen as normal in this culture. (Cc image from https://upload.wikimedia.org/wikipedia/commons/c/c0/Maori_matakite_Wai_Turoa_Morgan.jpg )
In the USA, Whaley (2004) suggests that cultural bias is responsible for the over-diagnosis of African Americans with schizophrenia. The incidence of diagnosed schizophrenia among this group is 2.1 per cent, while among Americans of European origin it is 1.4 per cent. Another view is taken by Cochrane and Sashidaran (1996), who argue that the poverty and racism experienced by immigrants and refugees is likely to lead to poor mental health. It is not their culture itself that is responsible, but their difficult life circumstances. However, due to cultural bias, it is often seen as being a specifically cultural problem, whereas it is the poverty and racism that are the problems.
Finally, there can be cases where schizophrenia may be less easily diagnosed because of cultural bias. Mesotho et al. (2011) found that while core symptoms of schizophrenia among the Sesotho speakers of South Africa may be similar to those in other cultures, there were also somatic symptoms such as headaches, palpitations, dizziness and excessive sweating. These can confuse the picture for a psychiatrist referring to either of the Western diagnostic manuals, the DSM-5 or the ICD-11, both of which are commonly used in South Africa.
References
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596
Cochrane, R. & Sashidharan, S. P. (1996) Mental Health and Ethnic Minorities: a Review of the Literature and Implications for Services. NHS Centre for Reviews and Dissemination/Social Policy Research Unit. Report 5. York: University of York
International Classification of Diseases, Eleventh Revision (ICD-11), World Health Organization (WHO) 2019/2021 https://icd.who.int/browse11
Lakeman, R. (November 2001). Making sense of the voices. International Journal of Nursing Studies, 38(5):523-31 DOI: 10.1016/S0020-7489(00)00101-2
Mosotho, L., Louw, D. & Calitz, F.J.W. (March 2011). Schizophrenia among Sesotho speakers in South Africa. African Journal of Psychiatry: 50-55
Whaley, A.L. (May 2004). Journal of Black Psychology, 30 (2): 167-186