Does Anxiety Cause Depression, or Depression Cause Anxiety?

Everyone knows that anxiety is related to depression, and that depression is related to anxiety. But that often seems to be the end of the discussion. Have you ever wondered how they are related or, specifically, whether certain anxiety disorders are more related to depression than others?

If you have, a recent meta-analysis assessed this issue.

Whether anxiety causes depression, depression causes anxiety, or they just co-occur together, is a long-standing debate. How do we figure it out? Well, a couple of researchers examined data from a ton of studies that met key criteria to answer this very question.

Key criteria: Must measure anxiety and depression over time. Is not an intervention study (as this would affect the natural course of the disorders). Involved original data collection.

Amazingly, they found 77 studies that met such criteria, with a good mix of child and adult studies! As such, this is a big study that summarizes data from more than 30,000 people.

Why is This Important?

If we know how anxiety and depression are related we can:

  • Develop interventions to address them together
  • Anticipate development of other problems over time
  • Understand the shared mechanisms involved in the disorders
  • Increase treatment precision
  • Hone interventions to prevent future relapse

What Did They Find?

Anxiety predicts later depression, and depression predicts later anxiety. Shocker! This supports a bidirectional relationship. But if we look more closely at the data it reveals some interesting stuff.

First, while anxiety and depression were strongly related, the strength of this relationship decreased over time. If someone is diagnosed with an anxiety disorder the correlations between anxiety and depression are much stronger than when people do not have an anxiety disorder. The exact same thing was found for depression.

However, they found that anxiety symptoms don’t predict depression, and vice versa. This is quite important because it potentially means that “catching” anxiety or depression symptoms early can lead to intervention that prevent other disorders from developing. It also normalizes that just having symptoms of one, doesn’t mean you will develop the other!

Here Is Where It Gets Really Interesting

They were able to break down which anxiety disorders predict depression and whether depression predicts specific anxiety disorders. These included Generalized Anxiety Disorder (GAD), Obsessive-Compulsive Disorder (OCD), Panic Disorder, Post-Traumatic Stress Disorder (PTSD), Social Phobia, and Specific Phobia.

They showed that if someone had an anxiety disorder they are 155% more likely to develop depression over time (anywhere from months to years) than if they didn’t have an anxiety disorder. This relationship was strongest over the short-term, but still true even for periods of time of more than 2 years.

If someone was diagnosed with depression the study showed that there is a 200% chance of being later diagnosed with an anxiety disorder, compared to someone who wasn’t diagnosed with depression. This effect only held up for less than 2 years.

1. If You Are Diagnosed With Anxiety, What Are The Odds Of Developing Depression?

Their analyses were a little confusing, and maybe that’s just because I don’t understand all of the statistics, or maybe it’s because there was some confusing information included. In one section they state that they found that all anxiety disorders predict depressive disorders. That being said, another analysis showed that PTSD was not a significant predictor of depression. This is only because, of the 4 studies that examined whether PTSD predicts depression, enough found no relation to cancel out those studies that did find a relation. (For you nerds, in other words the confidence interval was large and crossed 1). Still, I don’t know why the researchers didn’t explain this as it makes interpreting their findings difficult.

Below is a table showing the odds of developing depression based on having a specific anxiety disorder, compared to having no anxiety disorder. To give an example of what the data means, this shows that if someone is diagnosed with OCD, their chance of developing depression is 5.6 times more than if they did not have this diagnosis.

Odds of Developing Depression Based on Having a Specific Anxiety Disorder

OCD

5.6

PTSD

4.7 (not significant)

Panic Disorder

4.6

Social Phobia

2.6

GAD

2.6

Specific Phobia

1.7

 

2. If You Are Diagnosed With Depression, What Are The Odds Of Developing Different Anxiety Disorders?

OCD was the only anxiety disorder that a diagnosis of depression did not predict, although there were only 3 studies published to analyze this particular relation. Again, this is because enough studies showed no relation to cancel out studies that did find a relation. To describe what the below table shows, if someone is diagnosed with depression they are 6.1 times more likely to develop panic disorder.

Odds of Developing Different Anxiety Disorders Based on Having a Depressive Disorder

Panic Disorder

6.1

Social Phobia

6.0

PTSD

5.7

Specific Phobia

2.9

OCD

2.3 (not significant)

GAD

1.9

 

Depression Can Pose A Greater Risk For Certain Anxiety Disorders

I found this really interesting. If you look at the numbers in the tables above and compare them for each disorder, you can draw some cool conclusions.

You might not notice this, but a notable finding is that depression predicts diagnoses of social phobia and specific phobia much more strongly than either social/specific anxiety predict depression. To put it another way, depression is a stronger risk factor for development of social/specific anxiety than the other way around. This makes complete sense for a couple of reasons. One feature of depression is that it is hard to get out the house or be around others. We call this “low behavioral activation.” This can result in less socializing, more isolation, and eventually development of fear and avoidance of social situations that constitute social phobia. Clinically, this is not an uncommon series of events that I’m sure many people with depression can relate to. While the explanation is just a theory, it seems reasonable and is backed up by the data.

Why would depression more strongly predict specific phobia though? I have to admit, this doesn’t make intuitive sense to me. The authors argue that depression can be an adaptive evolutionary mechanism and by having both decreased behavioral activation and specific phobia then one is more likely to survive and reproduce. I don’t really like this explanation as it doesn’t seem satisfactory, but I don’t have anything better to offer.

OCD May Put You At Greater Risk for Depression

Although it wasn’t significant, I found it interesting to see that OCD is a much stronger predictor of depression than depression is of OCD. This again makes sense. They argued that this is because OCD is tied to perfectionism. I disagree as that’s far too narrow of an explanation. While it might be true, it’s much more likely to me that because OCD can be so interfering with life, due to the intrusive thoughts and need to do rituals, that the number of pleasurable life activities someone engages in is vastly reduced, leading to depression.

Implications

This study was a great summary of the research and showed that anxiety predicts depression and depression predicts anxiety. However, it also showed us a lot more detail than that. Specifically, if someone experiences depression then we need to be on the lookout for anxiety disorders too. We also need to make sure someone remains socially active and engaged in order to prevent development of social phobia. This would be consistent with a leading treatment for depression called Behavioral Activation. Likewise, if someone experiences significant anxiety they are at high risk of depression, possibly because it causes them to withdraw from situations. As such, treatment should occur promptly in order to minimize this effect.

The Mechanism Of Depression And Anxiety: How Do They Work?

The basic overarching mechanism this article alludes to, is that both anxiety and depression seem to promote avoidance of situations. By avoiding situations, anxiety can turn into depression, as a person’s life becomes more isolated and less rewarding. Similarly, depression promotes withdrawal and can result in the development of new fears and anxiety as various situations are avoided. This is incredibly helpful to know as it indicates that treatments need to focus on re-engaging in life activities that are valued by an individual. Evidence-based treatments for depression and anxiety are very active in working toward this specific goal as quickly as possible. This article provides support that by doing evidence-based treatments for depression and anxiety not only can you recover more quickly, but you can also prevent development of new difficulties.

Overall, this is all very interesting! If you experience or treat either depression or anxiety it can be helpful to know how they are specifically related and hypothesize the potential mechanisms involved. For example, knowing that OCD strongly predicts depression can make sure you don’t neglect to consider this. Given that the data was clear that anxiety and depression strongly predict one another, especially in the short-term, it indicates that you should pursue evidence-based treatment in order to experience lasting relief as quickly as possible.

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