Is depression really like diabetes? Yes – in more ways than you think

It’s often said that depression is just like diabetes.

The aim is usually to encourage people to speak up about their mental health problems, by pointing out that they’re no more worthy of shame than other illnesses.

The comparison seems to go down pretty well with most folks. But not with everyone. Some people hate it.

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So how much do the two conditions really have in common? A lot, I reckon. Their similarities run deep, but perhaps not in the ways that you’d considered.

To begin with, depression seems to me to compare more closely with Type 2 Diabetes than Type 1, for many reasons.

Whereas Type 1 always involves the same underlying problem – destruction of pancreas cells leading to a lifelong need for insulin – Type 2 is a more variable biological state, just like depression. In Type 2 Diabetes, high sugar levels are primarily caused by the body not being as responsive to insulin as it should be, but insulin levels are often low as well. Other hormones like glucagon and incretin are out of kilter too. This is akin to depression, in which we know that it’s not just serotonin that’s important at the biological level. Other neurotransmitters like noradrenalin and dopamine (and many others) are all involved.

The concept of depression sometimes gets criticised because it’s different for everyone, not like ‘real’ illnesses. But the biological state of any one person with diabetes won’t identically match that of any other any more than one depressed person’s brain will match another. They’re both illnesses with a lot of variation that we treat as one thing because the end results (high blood sugar or low mood) are relatively similar across people and treatments can be developed to tackle them.

Sure, diabetes has an objective test in blood sugar readings, whereas diagnosing depression relies heavily on rating someone’s sadness in at least a partially subjective sense, but just because mood is hard to measure doesn’t mean it’s not a real problem. And both blood sugars and mood ratings are tips of icebergs, the diagnostic variables that we choose to measure in conditions that affect much more. Diabetes will make you feel tired, give you headaches, make you drink lots and pee lots and eventually ruin your eyes and kidneys if left unchecked. Depression affects your sleep, appetite and sex drive and might lead to suicide.

Also, neither Type 2 Diabetes nor depression have one simple cause. Both are caused by a collection of individually small risk factors. With diabetes the big dangers are things like obesity, high cholesterol, poor diet and sedentary lifestyle, whereas with depression it’s things like recent adverse life events, a tough childhood and a lack of social support. Diabetes and depression both have a huge genetic component, but neither has a single-gene cause.

Taking things further, the treatment for both Type 2 Diabetes and depression is almost uncannily similar. The first step for both – and people never seem to know this – is not medication, unless the problem is severe. For diabetes it’s a change to a healthier lifestyle, whereas with depression it’s self-help and perhaps talking therapy. Both conditions can fully remit with those kinds of interventions, or partially remit, or remain a problem for life. When medication is needed it comes in the form of artificial chemicals that try to assist the body in doing what it does when it’s healthy. Drugs like metformin are first choice in Type 2 diabetes, and they certainly aren’t ‘natural’, but even injectable insulins aren’t the same as insulin produced by a real pancreas. Just like depression we don’t know who will respond to a particular diabetes treatment, how much, or why.

It’s ironic that some people think depression is something sufferers are to blame for and can fix for themselves (‘pull yourself together!’) when in reality it might be Type 2 diabetes with the risk factors and treatments that are most controllable by the person with the illness. It’s probably easier to shift your Type 2 diabetes by avoiding junk food, exercising and losing weight than it is to ease your depression by taking away life stressors like a busy job and magically undoing an abusive childhood.

So depression certainly isn’t identical to diabetes, but they do share a lot of common ground. They’re both illnesses with variable and complex biological states, tests which don’t show how widespread the problems can be, ranges of risk factors and treatments and unpredictable outcomes. Next time you hear someone say that ‘depression is just like diabetes’, you can agree with them – perhaps more than they’ll realise.

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