In preparing this Sharepost I had to decide whether it was going on the Anxiety or Depression site of Healthcentral.com. The title, you see, could just as easily have been ‘Anxiety - it's so Depressing,' and this probably tells you something about the nature of this post.

I blame lists and categories for all the confusion about anxiety and depression. Ever since someone in their wisdom decided that anxiety and depression were different everything you read treats them this way; but are they really so distinct? Naturally, I'm not talking about a low mood versus feeling a bit anxious, so much as symptoms that are extreme enough to be clinical in nature and that affect wellbeing.

Let me begin by throwing out a few statistics. It is estimated that the vast majority, over 85 per cent, of people with depression also have an anxiety disorder and over 30 per cent, have panic attacks. It is further estimated that over 50 per cent of people with an anxiety disorder have major depression but many more have symptoms of depression but that don't fit within the major depression category. The treatment of people with depression and/or anxiety often involves the use of selective serotonin reuptake inhibitors (SSRIs), the best known of which is fluoxetine (Prozac). In other words, not only do there appear to be more similarities than differences between anxiety and depression, but some of the major treatments are also the same. No wonder it's confusing.

Given the overlap in symptoms you might now be sharing the same thoughts as some other esteemed health professionals - which is, are anxiety and depression actually symptoms of a mental illness yet to be ‘discovered'? Interesting thoughts, but for the moment at least we're still in a situation where the two are regarded as distinct, but frequently appear together, known as comorbidity.

The next logical step is to take a look at the similarities and differences. In terms of the similarities between anxiety and depression there are lots. Just a handful of these serve to illustrate the point. Psychological and emotional symptoms of the two include feelings of fatigue, lowering of self-esteem and confidence, guilt, loss of interest in normal activities and difficulties in concentration. There are also similarities relating to sleep disturbances, appetite changes, physical symptoms such as headache, muscular pains and tensions and a general sense of feeling unwell.

With all these similarities, and more besides, it falls on the differences to explain why anxiety and depression are considered as separate entities. In many ways these are explained by degree of focus and extremes of thinking. For example, negative thinking is a feature of both anxiety and depression, but someone with depression tends to have a bleaker and all-encompassing outlook, whereas an anxious person without depression will focus negatively on specific issues but can often see light at the end of the tunnel.