The prevalence of depressive disorder among newly diagnosed patients with type 2 diabetes mellitus

The study population (n=186) consisted of 116 (62%) females and 70 (38%) males with a mean age of 51 years (range 27 to 80 years). Results showed that 13.4% (95% CI 8.5 – 18.3) had mild depression while 15.6% (95% CI 10.4 – 20.8) had moderate depression. There were no cases of severe depression. The proportion of females with depressive disorder was significantly higher than males. There were no significant association between the prevalence of depression and other socio demographic variables such as age, marital status, education, employment, income, ethnicity or religion.


Introduction
The prevalence of clinical depression and presence of elevated depressive symptoms are higher among persons with diabetes mellitus (DM) compared with the general population (1)(2)(3)(4).Two systematic reviews reported that prevalence of depression in patients with DM was 17.6% and 19.1% when compared to the prevalence of 10.7% in normative population (1,2).A meta-analysis showed that patients with type 2 diabetes have a 24% higher risk with a relative risk of 1.24 (95% CI 1.09-1.40) of developing depression (3).
The evidence suggests that the exposure/outcome relationship between these conditions is bidirectional and may change over the course of life.Two prospective studies in the U.S. and Japan have shown that depression doubles the risk of incident type 2 diabetes, independent of its association with other risk factors (5,6).A meta-analysis found that the relative risk for incident diabetes associated with baseline depression was 1.60 (1.37-1.88)(7).
The presence of comorbid depression in diabetes mellitus is associated with poor adherence to self-care regimens, such as glucose monitoring, diet, exercise and compliance with medication (8).In a recent WHO study, the greatest decrements in self-reported health were observed in those with both depression and diabetes, in comparison to those with depression and other chronic conditions such as angina, arthritis or asthma (9).Among patients with type 2 DM, depression was found to be strongly associated with higher health care use and expenditures, increased morbidity and mortality (10,11).Given the higher healthcare expenditure and increased mortality associated with depression, it is not surprising that clinical guidelines now recommend that all patients with diabetes undergo regular screening for depression (12,13).
Depression is also associated with behaviours such as smoking, physical inactivity and caloric intake that increase the risk of type 2 DM (14).It is also related to central obesity and to impaired glucose tolerance (15).
There is also evidence that depression can directly stimulate the production of proinflammatory cytokines that influence a spectrum of conditions including Diabetes Mellitus (17,18).DM may increase the risk of depression because of the sense of threat and loss associated with receiving this diagnosis, and the substantial lifestyle changes necessary to avoid developing debilitating complications.
A studydone in Chennai of subjects with impaired glucose tolerance, found the overall prevalence of depression to be 14.3% (19).The prevalence of depression in newly diagnosed patients with diabetes was 19.7% (19).The prevalence of depression was significantly higher among subjects with diabetic retinopathy, neuropathy, nephropathy and peripheral vascular disease as compared to subjects without these complications (20).A study in Pakistan revealed that depression is significantly associated with newly diagnosed type 2 DM among adults aged 25 to 60 years (21).The odds of mild depression among cases were 3.86 times the odds among controls (95% CI: 2.22-6.71),while the odds of moderate to severe depression among cases were 3.41 times the odds among controls (95% CI: 2.07-5.61)(21).A cross sectional study conducted among adult type 2 diabetes mellitus patients in Bangladesh showed the prevalence of depression to be 34.8%,which included 20.2% with severe depression and 14.6% with mild to moderate depression (22).
Although the relationship between type 2 DM and depressive disorder is well established, only a few studies have looked at newly diagnosed type 2 DM and depressive disorder.An understanding of the temporal relationship of depression in type 2 DM will be useful as an increased prevalence of depression from the onset may warrant early intervention.Thus the aim of this study was to describe the prevalence of depressive disorder in patients with newly diagnosed type 2 DM.

Methods
The study was conducted at the outpatient diabetic clinic of the District General Hospital, Chilaw from March 2012 to November 2012.Patients diagnosed with type 2 DM within a period of two months were recruited after informed consent.The cases of DM were operationally defined according to American Diabetic Association guidelines by a consultant physician (23).
This required the presence of any two of the following: Symptoms of polyuria (frequent urination) and polydispia (increased thirst and consequent increased fluid intake) plus random blood glucose level > = 200 mg/dl (11.1 mmol/l), or fasting blood glucose level > = 126 mg/dl (7.0 mmol/l) or 2 hour post prandial glucose level (> = 200 mg/dl (11.1 mmol/l) after 75 g glucose load.
The first author, who is a consultant psychiatrist, assessed all newly diagnosed patients with DM, for the presence or absence of depression.The diagnosis of a depressive disorder was established by clinical interview, based on ICD 10 criteria (24).Socio demographic data on age, sex, marital status, education, employment, income, ethnicity and religion were collected by an interviewer administered questionnaire.
In the absence of relevant Sri Lankan data, a minimum sample size of 169 was calculated based on an estimated prevalence of depressive disorder of 20% as reported in previously mentioned Chennai study by Poongathai et al (19).
The ethical clearance for the study was obtained from the ethical review committee of the Colombo South Teaching Hospital, Kalubowila.Eligible participants who gave written informed consent were included in the study.All the patients who were diagnosed with depressive disorder were referred to the nearest psychiatric unit for treatment.Statistical analyses were carried out using Statistical Package for Social Sciences (SSPS) version 17.
A significantly higher number of females (33.6%) had depressive disorder compared to the males (21.4%) (χ 2 =13.32; p =0.0002).The study revealed a high rate of depression (42.1%) among the over 65-year age group.The second highest rate was found among the 26-35 year age group.These differences were not statistically significant.There was no significant difference between marital status and the prevalence of depression (Table 2).
There was no significant association between education levels (p = 0.98) or income status and depression (p=0.21).Similarly the study did not show any significant association between ethnicity and religion with depression.In addition there was no association between current employment status and depression (Table 3).

Discussion
According to our findings, more than one fourth of the patients with newly diagnosed Type 2 DM had comorbid mild or moderate depressive disorder.An epidemiological study done by Ball et al. reported that the life-time prevalence of depression in a Sri Lankan population was 6.6% (25).A study conducted in the Northern province during the post conflict period (2013) revealed that the prevalence of major depression was 4.5% (95% CI: 4.1-4.9)and mild depression was 13.3% (95% CI: 12.7-13.9)(26).Therefore the prevalence of depression in our sample of newly diagnosed DM patients is much higher than the lifetime prevalence of depressive disorder reported for Sri Lanka and the prevalence of major depression in northern Sri Lanka during the post conflict period.
There are other studies done on similar populations with chronic physical illnesses in Sri Lanka.Sumanatissa et al reported that the prevalence of depression was 27.9% among 140 patients with chronic renal failure in the North Central province of Sri Lanka (27).Monaragala reported a prevalence of depression of 38.4% among 211 patients who presented to a tertiary cardiology center in the Central province following an acute myocardial infarction (28).Weerawardena studied 143 HIV patients and reported a 27.3% prevalence of depression (29).All these studies show a higher prevalence of depressive disorder among these diseased groups.
Asghar et al assessed depressive symptoms in 184 newly diagnosed diabetic subjects in Bangladesh using the Montogomery and Asberg Depression Rating Scale (MADRS) (30).They found that 29% of male and 30.5% of female participants with diabetes had depression, which is very similar to the findings of our study (30).
This study did not show any significant association between age and depression.However 42% of the elderly (over 65) group had depression.Raval et al reported that advancing age is associated with depression in patients with Type 2 DM in India and Khuwaja et al. too reported a higher incidence of depression among the elderly in a Pakistani population (31,32).It is reported that older patients face many challenges including social isolation, multiple diseases and disabilities; hence they may be more prone to developing psychological conditions.
This study showed a higher prevalence of depression among females than males and similarly, many studies done among newly diagnosed diabetes and long standing DM have reported higher incidence of depression among females (33,34).It is perhaps in keeping with population trends in general, that more females than males are diagnosed with depressive disorder (35).This study did not show any difference in depression according to marital status.However previous studies among those with long standing DM have reported a significantly higher prevalence of depression among unmarried participants with diabetes (36,37).

S Amarasinghe
Several studies have reported associations between lower educational level or lower socio-economic status and depression in DM (38)(39)(40).However our study did not find an association between depression and income or educational level.

Limitations
This study had a relatively small sample size and this may have influenced the detection of associations between depression and different demographic variables.The lack of a control comparison group is also a limitation, and prevents further exploration of the possible effects of diabetes on depression.

Conclusions
The findings of this study highlight the importance of screening for depressive disorder in patients with type 2 DM.All doctors working in the general medical setting should therefore be educated about the association of depressive disorder with DM and should be given adequate training to identify and treat depression in DM.

Declaration of interest
None declared

Table 1 .
Prevalence of depression in patients with type 2 diabetesThe prevalence of depressive disorder among newly diagnosed patients with type 2 diabetes mellitus

Table 2 .
Association between depressive disorder and personal characteristics P values are based on χ 2 tests for categorical variables and t-test for continuous variables.Rows (1) amalgamated for statistical purposes, Not living together (Divorced/ Separated/ Spouse Living Aboard/ Spouse dead)