Depression in young-onset type 2 diabetes

Depression is more common in those diagnosed with type 2 diabetes under the age of 40 than those diagnosed later in life. These findings from UK and USA data, reported in a recent issue of Diabetologia, highlight the need for clinicians to screen for depression, particularly in younger people diagnosed with type 2. Dr Susan Aldridge reports.

People with type 2 diabetes are at higher risk of depression than those without the condition. Meta-analyses of the literature suggest that the global prevalence of depression in type 2 diabetes has risen from 20% in 2007 to 32% in 2018. This is important, because depression in type 2 diabetes is associated with poorer adherence to treatment, lower quality of life and increased risk of both complications and mortality.

So, the connection between type 2 diabetes and depression is well known, but what is less clear is whether depression is more likely when someone is diagnosed at a younger age. So-called young-onset type 2 diabetes (YOD) – diagnosed between ages 18 and 39 – is on the increase in many countries, particularly the UK and USA. This is a matter of concern, because YOD is a more aggressive phenotype, with early development of complications. And as they age, with the longer duration of type 2, they are more likely to develop mental health problems and both microvascular and macrovascular complications, with a higher rate of hospitalisation than those with usual-onset type 2, which is diagnosed at age 40 and above. 

The relationship between age at diagnosis and risk of depression in type 2 is complex and needs further research to support effective management in primary care and to reduce healthcare costs. There is also the question of whether the presence of comorbidities like retinopathy and heart disease at diagnosis further increases the risk of depression.

Accordingly, Sanjoy Paul and colleagues at the University of Melbourne, together with William Polonsky, a leading expert in diabetes psychology, have carried out a study which compares the risk of depression in YOD and usual-onset diabetes and whether this is affected by the presence of comorbidities. They also looked at time trends in depression across the age groups. They drew upon electronic medical records (EMRs) from primary care from both the USA and the UK for their data. A total of 230,932 people from the UK and 1,143,122 people from the USA were included in the study. Comorbidities recorded were any cardiovascular disease, microvascular disease, obesity or cancer. The presence of comorbidities, as expected, was highest in the 70–79 group at 70% (UK)/65% (USA) and, in the YOD group, it was 36%/59%.

Trends in depression

The prevalence of depression has gone up over all age groups with type 2 diabetes, in both the UK and the USA, with annual increase rates of 3.8%/2.8%. A similar trend was noted for incidence rates. 

In both the UK and the USA, YOD was associated with a higher risk of developing depression than usual-onset diabetes. In the UK, men with YOD had a 23 to 57% higher risk of depression compared with those who were older. The corresponding figure for women was a 20 to 55% higher risk. These increased risks were similar whether or not comorbidities were present at the time of diagnosis. In the USA, the increased risk for YOD was 5 to 17% in men and 8 to 37% for women, again compared with usual-onset diabetes.

Targeting depression

This study, involving 1.4 million people with type 2 diabetes from population-based EMRs from two different healthcare systems gives us an important new insight into the risk of depression according to age at diagnosis. It is the first to explore the population-level trend in depression prevalence at the time of type 2 diabetes diagnosis across both sex and age groups.

First of all, depression has increased over time in all age groups. And, second, those with YOD have a significantly higher risk of depression compared with those with young-onset diabetes, regardless of the presence of comorbidities at the time of diagnosis. The authors note that their depression prevalence figures are similar to those found for Europe and the USA in other studies. Prevalence and incidence of depression are also significantly higher among women in both the UK and the USA and across all age groups.

This study shows that there are mental health implications of developing diabetes at an early age, whether or not comorbidities are present. The underlying pathophysiology of depression in people with type 2 has been investigated. Risk factors, including obesity, may play a role. Future studies should look into the effects of risk factors before and after diagnosis in different age groups, sex and ethnicity, to explore the underlying causes of depression in YOD further.

And healthcare professionals shouldn’t wait for this research. There is enough in the findings of this new study to highlight the importance of proactive engagement of primary care teams in mental health management of those diagnosed with type 2 diabetes. It’s well worthwhile preventing or catching YOD-related depression, not just for the patient’s sake, but to reduce healthcare costs. One survey from the USA revealed that people with type 2 and depression run up double the expenditure compared with those who have diabetes but no depression.  

Then there is the increase in depression over time in all age groups. This might be because of increased awareness of depression in diabetes as more research and education on the subject emerges. And better record keeping with the transition to EMRs may have allowed for more cases of depression to be captured. Of course, the under-reporting of depression is known to be a problem globally, so the figures here might actually be an underestimate.

Proactive management of comorbid depression in type 2 diabetes, at any age, should involve screening, early diagnosis and prompt treatment with medication and/or talk therapy. This is a worthwhile investment, as it could lead to better glycaemic control and control of other risk, delayed onset of complications and lower healthcare costs. Innovative approaches to identify subgroups of patients most at risk of depression would also be useful to target early intervention.

So, the authors strongly recommend proactive mental assessment in primary care from the time of type 2 diabetes diagnosis, regardless of age or the presence of comorbidities. This should become an essential part of diabetes care. 

To read this study, go to:
Dibato J, Montvida O, Ling J, Koye D, Polonsky WH, Paul SK. Temporal trends in the prevalence and incidence of depression and the interplay of comorbidities in patients with young- and usual-onset type 2 diabetes from the USA and the UK. Diabetologia 5 September 2022. https://pubmed.ncbi.nlm.nih.gov/36059021/

Any opinions expressed in this article are the responsibility of the EASD e-Learning Programme Director, Dr Eleanor D Kennedy.