Psychologists have noted that some forms of mental disorders are more common among lower socioeconomic groups. which model of mental illness is best able to account for this observation?

The correct answer is the sociocultural model of mental illness. 

The sociocultural model of mental illness is a theory of mental illness which claim the social and cultural context one is subject to has a direct influence on his or her mental health. According to this model, mental illness or abnormality is a socially constructed phenomenon defined by a society's criteria and definition of normal or abnormal behavior. According to the sociocultural model of mental illness, some forms of mental illness are more common in certain socioeconomic groups compared to others.