
According to criteria from the 10th edition of the International Classification of Diseases depression has three main symptoms:
- Low mood;
- Loss of interest in everyday activities;
- Fatigue or low energy.
If one or more of these symptoms are present, it is important to find out if there are any additional symptoms to determine the severity of depression. These include:
- Disturbed sleep;
- Poor concentration;
- Low self-confidence;
- Poor or increased appetite;
- Ideas or acts of self-harm or suicide;
- Slowing of movements;
- Guilt or self-blame (National Institute for Health and Clinical Excellence, 2009).
Severity of depression is assessed by determining the number and severity of the depressive symptoms outlined above, usually over a minimum of two weeks:
- <4 - no depression;
- ≥4 - mild depression;
- 6-7 - moderate depression;
- ≥8 - severe depression.
Categorising in this way may direct the type of treatment that is provided. As a rule of thumb, a depressive episode can be distinguished from a period of sadness by symptoms lasting longer than two weeks, occurring on most days of the week and there being a distinct loss of functioning.
Risk factors for depression
Risk factors for depression in people with diabetes are often similar to those for the general population. For example, depression is more common in women, younger people, those who have had stressful life events, people who live alone or have low levels of social support, those with lower socioeconomic status and those with additional health problems (usually affecting older people) (Winkley, 2008).
In addition to these common risk factors, particular factors are associated with depression in people with diabetes:
- Diabetes complications;
- Longer duration of diabetes;
- Severe diabetes;
- Little physical activity;
- Dependency on others;
- Persistent poor glycaemic control;
- Problems with hypoglycaemia;
- Patients with type 2 diabetes who are treated with insulin (Winkley, 2008).
Depression is a risk factor for type 2 diabetes but diabetes is also a risk factor for subsequent depression (Nouwen et al, 2010). This suggests the two conditions share common pathways as both are associated with physical inactivity, obesity and cardiovascular disease.
Course of depression
Few studies have examined depression in people with diabetes but the available evidence suggests depression is more chronic in people with diabetes than in general population samples (Winkley, 2008). For example, 64% of people with both depression and diabetes have depression with a relapse-remitting course (relapse is defined as a worsening of mood within a nine-month period), 15% never recover from their depression, and only around 20% recover fully (Lustman et al, 1997).
Adverse effects of depression
The effects of depression can be detrimental to health, quality of life and personal relationships. However, when people also have diabetes, it is common for them to increase their use of health service resources and reduce their adherence to their diabetes self-management programme, such as eating less healthily, reducing physical activity and not adhering to oral medications. Cognitive dysfunction can also be problematic and is common with diabetes and depression.
It is not fully understood why risk of mortality is higher for people with diabetes and depression, but there is consistent, international evidence suggesting a link. In both the UK and US, studies confirm that affected patients are two to five times more likely to die earlier when they have both comorbid conditions (Ismail et al, 2007; Black et al, 2003).
In the UK, a cohort of patients with their first diabetic foot ulcer and with minor and major depression were three times more likely to die at 18-month follow-up and these effects persisted at five years (Winkley et al, 2012; Ismail et al, 2007). In the US Pathways study, a cohort of 4,385 people with type 2 diabetes followed up for three years found a 1.67-fold increase in mortality in those with minor depression and a 2.3-fold increase in those with major depression (Kat