Anxiety and depression: Are they co-morbid?

Written by: Dr Stephanie Thornton | Published:
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An estimated one in 10 teenagers have mental health problems, with a high prevalence of anxiety and depression. In this five-article series, Dr Stephanie Thornton advises schools and teachers. In part two, she asks if anxiety and depression are co-morbid or one syndrome

As we discussed in the first article in this five-part series, it is widely accepted that around 10 per cent of teenagers have mental health problems, the majority being diagnosed with anxiety, depression, or both. Many experts believe that that figure is actually much higher, and rising: we do not really know, since no major review has been undertaken for some time (Beesdo et al, 2009).

If you search online for depression and anxiety you will find many sites offering advice on how to identify these issues: depression has these symptoms, anxiety has those. And in a professional context, we generally treat these as separate disorders: that is how most diagnostic systems and textbooks present the issues at the moment.

However, the situation is far less straightforward and far more controversial than this simple dichotomy suggests. There is actually considerable debate in this area.

In fact, the diagnosis of all mental health problems is far less straightforward than is generally supposed. Physical health problems sometimes present the same complexities of diagnosis, but in many cases, there is some definitive virus, bacteria, cellular change or the like that allows us to define a given physical illness and identify it very precisely.

Anxiety and depression: A five-part series by Dr Stephanie Thornton

Part 1: Anxiety and depression: The new normal? March 2020:
Part 2: Anxiety and depression: Are they co-morbid? April 2020:
Part 3: Anxiety and depression: When should we intervene: May 2020:
Part 4: Anxiety and depression: Managing anxiety in the classroom: June 2020:
Part 5: Anxiety and depression: Managing depression in the classroom: July 2020:

With a very few exceptions (such as the degenerative mental problems associated with Huntington’s, tertiary syphilis or Alzheimer’s), there is no such objective or physiological basis for a definitive diagnosis for mental health problems.

In the realm of mental health, diagnostic categories have evolved through observing statistical regularities in patterns of symptoms, and making the best sense of those that we can. The results are often controversial.

For example, in recent years, there has been considerable emphasis on ever more exact definitions of particular varieties of anxiety: general anxiety disorder, specific phobias, agoraphobia, panic disorder, or post-traumatic stress disorder and so on. Yet the advantages of making such specific and detailed diagnoses is challenged by some experts.

Specific anxieties seldom occur in isolation: in fact, it is far more common for several strands or types of anxiety to occur together (Bandelow et al, 2015), suggesting that a more generalised diagnosis may be better.

Some experts have also argued that, given the current lack of understanding of how co-morbid forms of anxiety may interact, a very specific diagnostic interpretation of an individual’s anxiety may lead to too narrow a focus in treatment, leaving other specific or more general aspects of anxiety unaddressed.

A further argument comes from the fact that effective treatment regimes, both drug-based and counselling or CBT-based, have substantial overlap across many forms of anxiety, again undermining the value of making detailed, specific distinctions in diagnosis. So, would we do better to have a more unitary view of anxiety?

Against this view is the discovery that some types of intervention can be beneficial for some types of anxiety – but may be detrimental in other types. The clearest example is that mindfulness meditation is somewhat helpful in various forms of anxiety, but can be counter-productive or even damaging in PTSD (Lustyk et al, 2009). So in at least some cases, more specific diagnosis may have benefits.

The debate as to where to draw the diagnostic lines in common mental health issues goes far beyond the dissection of anxieties. In fact, over the past 10 years there has been debate among researchers as to how to define the distinction between the apparently different syndromes of anxiety and depression – and whether this is a useful thing to do.

Perhaps surprisingly, there has been debate among researchers as to whether what is presently defined as “generalised anxiety disorder” (GAD) might be better interpreted as a depressive rather than an anxiety disorder (Beesdo et al, 2009).

The case for a re-interpretation of GAD seemed quite strong a few decades ago, though this debate among researchers did not really emerge into the mainstream of popular understanding or clinical work. However, on the basis of a large review of studies, Beesdo et al (2009) concluded that GAD is still better interpreted as primarily an anxiety disorder. But this debate illustrates the controversies concerning the diagnoses of depression and anxiety.

From many points of view, the distinction between anxiety and depression is less clear cut than is often assumed, or is presented by online advice sites.

Anxiety and depression very often occur together (Hirschfeld, 2001). Up to 60 per cent of those who are depressed are also anxious, and the same percentage of those presenting as anxious are also depressed (and these figures may be conservative, reflecting the practice in diagnosis that assumes the problem is predominantly one or the other).

In common sense terms, it is easy to understand how depression and anxiety may be interwoven, each both triggered by and exacerbating the other: to be anxious is intrinsically depressing, and the many woes that come with depression might easily trigger anxiety.

But the connection between the two may be more profound than this suggestion of probable co-morbidity implies. For example, there is neurological research suggesting that the same neural patterns underlie both anxiety and depression, and this has been hailed as a possible basis for new and better, more targeted drug treatments (Magalhaes et al, 2010). But this intriguing research is still in early days: the neurology has only as yet been explored primarily in mice.

More pragmatically, it is clear that at least some of the symptoms of anxiety and depression are the same - for example, sleep disturbances are common to both. And equally, there is clear overlap in the risk factors that dispose an individual to suffer from depression or anxiety, including familial and situational experiences (Beesdo et al, 2009).

In light of these commonalities across anxiety and depression, and the high rates of co-occurrence, some researchers suggest that rather than regarding anxiety and depression as separate co-morbid conditions, we should regard them as different facets of a single syndrome (Beesdo et al, 2009).

But this may be an over-simplification of very complex phenomena. Not every anxious person is depressed, and not every depressed person is anxious. And in their large-scale study, Beesdo et al (2009) concluded that, for all the commonalities, anxiety and depression do have some distinct characteristics, justifying the use of two separate diagnoses.

Nonetheless, there is continuing research debate as to the diagnosis of anxiety and depression. Anxiety and depression rarely occur in pure forms (Jacobi et al, 2004), and the sheer frequency of co-occurrence, and the overlaps between anxiety and depression raise questions. Is there a case for sometimes diagnosing depression, sometimes diagnosing anxiety, and sometimes explicitly diagnosing a third category of “anxiety-with-depression”?

This threefold diagnosis maps onto what we know about the efficacy of treatment. Anxiety without depression, and depression without anxiety respond to different treatments. And both of these “uncomplicated” conditions respond better to treatment than is the case for co-occurring anxiety and depression.

Anxiety-with-depression is far harder to treat, far more likely to result in chronic illness, and far slower to respond to treatment (Hirschfeld, 2001). Directly identifying this mixed pattern of mental health problem as a specific diagnosis may focus attention on the need for more powerful interventions in such cases, and help the discovery of new patterns of treatment that will allow more effective interventions.

  • Dr Stephanie Thornton is a chartered psychologist and former lecturer in psychology and child development. To read Dr Thornton’s previous articles in SecEd, including in this series, go to

Further information & research

  • Bandelow & Michaelis: Epidemiology of anxiety disorders in the 21st century, Dialogues in Clinical Neuroscience, September 2015.
  • Beesdo, Knappe & Pine: Anxiety disorders in children and adolescents: developmental issues and implications for DSM-V, The Psychiatric Clinics of North America, 2009:
  • Hirschfeld: The comorbidity of major depression and anxiety disorders: Recognition and management in primary care, Primary Care Companion, Journal of Clinical Psychiatry, December 2001.
  • Jacobi et al: Prevalence, comorbidity and correlates of mental disorders in the general population: Results from the German Health Interview and Examination Survey, Psychological Medicine, May 2004.
  • Lustyk et al: Mindfulness meditation research: issues of participant screening, safety procedures, and researcher training, Advances in Mind Body Medicine, March 2009.
  • Magalhaes et al: CRF receptor 1 regulates anxiety behaviour via sensitization of 5-HT2 receptor signalling, Nature Neuroscience, April 2010.
  • SecEd/Thornton: Anxiety and depression: The new normal? (part one of this series), March 2020:


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