Who first coined the term comorbidity?
B. The term comorbidity refers to the existence of two different diagnoses at the same time in an individual. In psychiatric epidemiology, comorbidity is a rule rather than exception. This high degree of comorbidity is partly due to the overlapping nature of diagnostic entities in psychiatry. Comorbidity in epidemiological research throws light onto possible aetiological underpinnings and meaningful outcome variables. Feinstein coined the term comorbidity.
The various types of comorbidity are:
Reference:
Which of the following is the best estimate of the incidence of schizophrenia if a rigorous systematic review of various epidemiological studies to date is carried out?
A. The rigorous, systematic review mentioned in the question was carried out by McGrath and colleagues. Prior to this, in 1986, the WHO published results from the International Pilot Study on Schizophrenia from seven countries; incidence of ICD 9 schizophrenia was estimated to be around 16 to 42 per 100 000 in a year. When schizophrenia was narrowly defined, this rate dropped to 7 to 14 per 100 000. McGrath et al. showed a fivefold difference in the incidence rates of schizophrenia across various sites in their systematic review and meta-analysis of various epidemiological studies on schizophrenia. According to this work, it is concluded that the median global incidence rate of schizophrenia is 15 per 100 000; but this global rate is not as meaningful as site-specific rates due to the degree of variation demonstrated. This view is endorsed by the AESOP study, which showed significant variation in incidence of schizophrenia among three major cities in England.
The male to female risk ratio for developing schizophrenia is calculated to be which of the following values?
B. The male to female difference in incidence of schizophrenia is estimated to be around 1.4: 1, with more males being diagnosed with the disease. The male excess persists even when factors such as age range and diagnostic criteria are taken into account; but interestingly this difference is not borne out when considering prevalence rates, suggesting that different factors exist in predisposing and perpetuating the illness. It may be related to males having higher mortality rates than females with schizophrenia or increased predominance of females in late-onset schizophrenia.
The risk ratio for developing schizophrenia in migrants compared to a native population is:
C. Being born in an urban area increases the risk of schizophrenia twofold compared to individuals born in a rural area. Living in a city is also noted to increase incidence of schizophrenia. The incidence of schizophrenia is three to fi ve times more common in migrants than a native population (median 4.6); this difference reduces to 1.8 when considering prevalence rates. Fluctuations in schizophrenia incidence have been reported over many decades. This may be related to changing structure of the population. Irrespective of broad or narrow definitions, the incidence of schizophrenia has definitely increased in certain urban areas over the last 40 years.
The probability of developing a disorder anytime throughout the life course of a birth cohort is called:
B. Lifetime prevalence needs to be distinguished from lifetime morbid risk (LMR). LMR is the probability of a person developing the disorder during entire period of their life (often a specified period, defined by the life expectancy of the population studied). LMR includes the entire lifetime of a birth cohort, both past and future, and includes those deceased at the time of the survey.
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