Why are anxiety and depression so correlated?

Do you know what the two most common types of mental health challenges in the entire world are? The answer is one, anxiety, and two, depression. By the World Health Organization’s 2019 estimates, about 300 million people in the world have anxiety disorders, and about 280 million people have depression. Truly staggering numbers. Anxiety disorders, such as generalized anxiety disorder, are characterized by worry, nervousness, and fear. At first glance, these seem to have nothing to do with depressive disorders like major

Depression, which are characterized by hopelessness, loss of motivation, and lack of enjoyment of activities. Clearly, symptoms like worry and fear are totally different from hopelessness, sadness, and lack of pleasure. Right? It might even seem that anxiety and depression are opposites in a way. When you’re afraid, your heart is pounding. You’re highly motivated to get away from something scary. Whereas, when you’re depressed, you tend to be in a subdued, low energy state, lacking in motivation. you don’t want to do anything at all.

And yet, when we were conducting a study on depression and anxiety involving hundreds of people, we found something that blew our minds. We measured participants depression levels using a symptom questionnaire called the PHQ9. And we measured their anxiety levels using a symptom questionnaire called the GAT 7. These are extremely standard and commonly used ways of measuring depression and anxiety. And yet, despite these disorders seeming so different from each other, depression and anxiety could barely be distinguished in our

Data. People’s depression scores and anxiety scores had a 08 correlation. A correlation so high you almost never see it in psychological research. In fact, that’s only a little bit smaller than the correlation between the height of identical twins, which is about 0.9. Depression and anxiety are so correlated that it has even led some people to call for combining them into a single disorder, such as MAD, which stands for mixed anxiety depressive disorder. So, should anxiety and depression be merged

Into a single disorder? And why on earth are they so correlated to each other when at first glance they appear to be about unrelated things? The first part of the answer, though it’s far from the whole story, is that depression and anxiety have some symptoms in common. Both depressed and anxious people tend to struggle with sleep issues, tiredness, difficulty concentrating, and irritability. In other words, both depression and anxiety can have similar effects on people. That means that if

You’re not careful and you try to measure depression and anxiety just using their symptoms, you may end up concluding that they’re even more linked than they really are simply because they share some symptoms in common. There are also patterns of thinking and behaving that are similar between these two conditions. But when you look at these closely, there are subtle and important differences that distinguish these patterns. For example, both anxiety and depression are associated with repetitive negative thoughts. But

Negative thoughts connected to anxiety tend to take the form of what ifs such as what if I get fired from my job? What if my partner dumps me? Or what if this mole turns out to be cancer. Negative thoughts related to anxiety are typically worries about the future. On the other hand, the sort of repetitive negative thoughts that people who are depressed typically have are different. Rather than being worries, they are ruminations about the past or about

One’s own worth. Depressed people might obsess over their past mistakes, repetitively tell themselves they’re worthless, or think about how nothing in their future will ever matter. So, we’ve seen that anxiety and depression both typically involve repetitive negative thoughts, but these involve different sorts of negative thoughts. We see a similar pattern with behaviors. Both anxiety and depression frequently involve avoidance behaviors such as cancelling plans or not handing in work, but they do so for different reasons. People high in anxiety typically avoid

Things out of fear. They may cancel plans because they feel anxious about seeing people. Those with depression, on the other hand, are more likely to avoid things because they see them as pointless or meaningless or doomed to fail. They may cancel plans because they assume they aren’t going to enjoy those plans or because they assume those people won’t actually enjoy being around them. Taking a step back, we’ve seen so far that anxiety and depression are extremely correlated, that they share

Some of their symptoms, and that they both lead to negative thoughts and avoidance behaviors. But there are two other important reasons that depression and anxiety are linked that we haven’t yet seen. The first is that they can have common causes. Difficult childhood experiences such as abuse, neglect, and lack of opportunity can increase the chance of both anxiety and depression later in life. This creates a correlation between the two disorders. It’s also believed there are some genes

That can simultaneously be a risk factor for both depression and anxiety, further linking the two disorders. Some studies show a high genetic correlation between anxiety disorders and major depression. The last reason that anxiety and depression are linked is that they can actually cause each other. How so? Well, when people are depressed, they often lack motivation and struggle to accomplish things as easily as they usually can. They may start avoiding other people as well. These behaviors can create increasing life challenges.

For instance, increasing the risk of being fired from work or having friction in relationships. Of course, the risk of being fired and relationship friction are likely to cause anxiety. Hence, depression can cause anxiety. But what about the reverse? Well, when people are suffering from severe anxiety, they often avoid things that are valuable to them because of fear. This can lead not only to missing out on valuable opportunities, but also can make life feel increasingly closed off. This can

Leave anxious people with less enjoyment in their lives and give them the sense they can’t get the things in life that are valuable to them anymore, which can cause them to be depressed. So now we’ve seen that not only do depression and anxiety share symptoms, but they can be caused by the same things and they can actually cause each other. But what then fundamentally are the real differences between these two disorders? To help figure this out, we collected data on

500 people and measured the depression and anxiety of each person, being careful to avoid making these measurements using symptoms that are side effects of both disorders. Because depression and anxiety are so correlated, pretty much any symptom that correlates with depression will also correlate with anxiety and vice versa. So we carefully conducted a statistical analysis to figure out which symptoms are fundamentally correlated with depression even when you adjust for how anxious people are, which are fundamentally correlated with anxiety

Even when you adjust for how depressed people are, and which are fundamentally related to both depression and anxiety. Here’s the result. As expected, there are some symptoms that are truly associated with both disorders, such as being distracted by your thoughts, getting stuck on issues without being able to move on, and assuming that when one thing goes wrong, other things are likely to go wrong as well. But we can also see there are some symptoms that are fundamentally connected to anxiety

Only. Worry, being overwhelmed by these worries and frequently thinking about scary what if scenarios are really parts of anxiety, not depression. Additionally, being easily startled and a need to know what the future has in store are also fundamental aspects of anxiety, not depression. On the other hand, having a low opinion of yourself or believing you are undeserving of respect are fundamentally connected to depression, not anxiety. And seeing events as having no meaning or purpose and seeing most things as being boring

Are also fundamentally connected to depression, not anxiety. So, are anxiety and depression the same disorder? No, they’re not. Despite their extremely high correlation and the fact that many anxious people are depressed and many depressed people are anxious, they are not the same. Some people have pure depression with little or no anxiety and some have pure anxiety with little or no depression. They are different disorders at their core. In my opinion, at their deepest level of description, anxiety is

About feelings of uncertainty of whether something of value to you will be lost. Whereas depression is about seeing your own value or the value of the future as having already been lost. They are deeply linked disorders that share some of the same symptoms that are caused by some of the same factors and that can actually cause each other, but anxiety and depression are not the same. If you found this interesting, I’d really appreciate it if you’d subscribe to this

Channel. You can also learn a great deal more about this topic by checking out our in-depth article at clearerthinking.org.