What Causes Depression and Why Do We Get Depressed?

What causes depression? First we’ll look at a simple diathesis-stress model of depression. Under the diathesis-stress model, if our levels of predisposition or vulnerability to depression, plus levels of life stressors, exceed our tolerance levels, then we become depressed.

Then we’ll learn a more comprehensive model of depression proposed by Aaron Beck. Aaron Beck is the founder of cognitive behavioral therapy (CBT), and the person most responsible for how we treat depression with psychotherapy. In Beck’s model, there are a number of factors that predispose us to depression, such as genetics, childhood adversity, biology and negative cognitive bias.

These all contribute to the formation of a negative cognitive triad. The negative cognitive triad is a set of negative core beliefs about:

  • Ourselves as worthless, unlovable and/or helpless
  • The world and other people as hostile, unfriendly and/or rejecting
  • The future as hopeless

This negative cognitive triad then leads us to interpret life stressors in ways that can trigger depression.

After going over Beck’s model of depression in detail, we’ll consider the implications of this model for treating depression, and reducing vulnerability to depression and depression relapse.

What Causes Depression and How Do We Get Depressed

This transcription was auto-generated by YouTube. I’ve only added minimal editing, so I apologize for any errors, run-on sentences, etc.

What causes depression and how do we become depressed? Well we don’t know exactly what causes depression in the way we know that for example the influenza virus causes the flu, but we’re going to learn a model of depression and how depression comes about and then see what we can take away from this model that can help us treat depression and make it less likely that we become depressed.

So a common explanation for how we develop mental health issues in general is what’s known as the diathesis stress model, diathesis meaning a predisposition or vulnerability to something, and stress just meaning stress, a stressful situation or circumstance or experience or event, or the accumulation of a number of stressors.

And then if our levels of predisposition plus our levels of stress exceed what we’re able to tolerate then that predisposition becomes activated and we become, for example depressed. And we all have different levels of predisposition, and we’re all able to tolerate different levels of predisposition plus stress, so the amount of stress necessary to trigger depression will be different for everyone.

So we can imagine having a cup of a certain size that represents our levels of tolerance. And if we pour into this cup more predisposition plus stress than the cup is able to hold, our tolerance cups start to overflow and we become depressed.

So that’s a general model of how we get depressed, now let’s look at a much more detailed model, proposed by Aaron Beck, the person who founded cognitive behavioral therapy, and whose research is most responsible for how we now treat depression with psychotherapy.

So what predisposes someone to depression? First there are genetic risk factors and or some sort of childhood trauma or negative childhood experiences, that lead us to develop increased biological reactions to stress and cognitive biases that prioritize and emphasize negative experiences and information.

And these can lead to the formation of what’s called the negative cognitive triad, which are negative beliefs about ourselves, about the world and other people, and about the future. And these beliefs affect how we interpret or appraise various life situations and stressors and how they impact us. So this is the diathesis side of the equation, the things that predispose us to depression.

And then if in conjunction with our predisposition we’re faced with more stress than we’re able to tolerate, this combination of predisposition plus stress leads to depression.

And then the symptoms of depression feed back into our negative beliefs and reinforce them which prolongs our depression and makes us more vulnerable to depression in the future. And these symptoms can also act as stressors themselves that feed back into our depression.

So now let’s break this down and look at each of the individual components of this model in more detail. And there are a few parts of this that are a little dry so i’ll try to get through them quickly.

So first up genetics. Although we know that depression can have a genetic component there’s no consensus about the specific genes that can predispose us to depression. But for example there’s evidence that the short allele or genetic variant of 5-httlpr is associated with higher levels of depression following a life stressor. 5-htt is a serotonin transporter and is a main regulator of serotonin in our brains and there’s a lot of evidence that links lower levels of serotonin to depression. And there are other genetic variants that may predispose us to depression and depression is probably poly genetic or influenced by more than one gene.

Now genetics alone is not enough to make us vulnerable to depression: not everyone with genetic risk goes on to develop a predisposition to depression. But also genetic risk isn’t necessary in order to become predisposed to depression: we can become vulnerable to depression from childhood developmental and environmental factors alone. Childhood adversity makes us vulnerable to depression for example the loss of a parent at an early age is a big risk factor as is childhood neglect or abuse negative interactions with parents and any other type of major childhood stress or adversity.

These genetic risks in childhood developmental factors lead to biological differences in how we react to stress and cognitive biases in how we process information increased biological reactivity to stress, in other words our bodies react more to stress, predisposes us to depression.

Depression is correlated with hpa access Dysregulation. The hpa axis is a network of hormones that gets activated by stress and produces the stress hormone cortisol, and people with depression exhibit an elevated cortisol response to stress.

In people with depression there’s also an elevated activation of the amygdala region of the brain in response to stress. The amygdala plays the central role in emotional processing and has an activating influence on the hpa axis. And both the short allele variant of 5-httlpr and adverse childhood experiences are associated with increased amygdala reactivity.

Another thing that predisposes us to depression is that we selectively pay attention to negative information and experiences and ignore positive information. We also have a memory bias and remember negative information more readily than positive information. And we’re more sensitive about making mistakes and receiving negative feedback.

And while this type of negative cognitive bias predisposes us to depression, depression also causes cognitive biases in favor of negative information, resulting in a negative feedback loop or vicious cycle that can prolong or intensify depression and make us more vulnerable to depression in the future.

And adverse childhood experiences predict these sorts of negative cognitive biases later in life. And the 5-httlpr short allele is also associated with these types of cognitive processing biases as is increased amygdala activation.

So now let’s look at the heart of this model. According to Aaron Beck’s research into the relationship between thinking and depression, what makes us most vulnerable to depression is the presence of what he calls the negative cognitive triad, which is a set of negative core beliefs about ourselves as helpless unlovable or worthless; and negative core beliefs about the world and other people as hostile unfriendly or rejecting; and negative core beliefs about the future comprised of hopelessness and pessimism. And these negative core beliefs develop as a result of our negative information processing biases and our increased biological reactivity to stress as well as directly out of our adverse childhood experiences

Now our core beliefs affect how we interpret information, and so given a similar set of circumstances and similar information, our cognitive appraisals and what we make of this information and how we interpret it will be different depending on our core beliefs.

So for example let’s say we text a friend and ask them to meet up for coffee and they respond, sorry I’d love to but I’m too busy right now, let’s do it sometime soon.

So if we don’t hold negative core beliefs about ourselves about the world and other people, or about the future, our cognitive appraisals or interpretations of this situation could be something straightforward and relatively neutral like, they’re just too busy to meet up right now but we’ll probably see each other soon. Or maybe our beliefs about the world and other people would lead us to appraise this situation as something like i guess they don’t want to hang out and they’re just being polite.

But if we have really negative core beliefs these could lead to a cognitive appraisal along the lines of, of course they don’t want to hang out with me I’m such a loser nobody wants to hang out with me. I thought we were friends but i guess i just can’t count on anyone. Everyone always lets me down. Nobody’s ever going to really want to be my friend, and I’m going to be lonely and alone forever.

And so it’s not the stressor alone that determines our cognitive appraisals about the situation, but how that stressor interacts with our core beliefs. If we have that negative cognitive triad of negative core beliefs we end up interpreting situations like this in very negative ways that feel really bad and can set us up for becoming depressed.

But these negative cognitive appraisals alone aren’t enough to make us depressed. Whether or not we become depressed will also depend on the nature of the stressor or negative experience or life event that we’re exposed to.

So what kind of stressors can trigger depression? Usually it involves some sort of loss or perceived loss. Interpersonal loss is a common trigger. It could be the loss of someone we love through death or the breakup of a relationship. Or it could be the loss of our health or vitality: there could be a serious or chronic health issue where we could just start feeling older or we get injured and can’t do some of the things we used to enjoy or that are important to us, or we can’t do them as well as we used to be able to.

Or we could get laid off or fired or lose our jobs. Or it could be the perceived loss of control over certain aspects of our lives. Or a loss of status or acceptance among our peers or colleagues or any group we identify with.

What constitutes a loss capable of triggering depression will be different for everyone depending on what we value and what’s important to us. And it may not just be one thing that triggers depression: there may be various contributing factors going on at the same time; or just the accumulation of a number of factors.

And whether or not this loss or stress triggers depression will depend on how severe it is and how we interpret the loss. We’re particularly vulnerable to losses that negatively affect our self-image and result in a loss of self-esteem self-confidence or self-worth or to a loss of purpose direction or meaning in our lives

So going back to the example of texting a friend to hang out and they decline that situation in itself probably isn’t going to be a strong enough stressor to trigger depression. But imagine if instead the situation were something like a partner breaking up with us. That’s a much bigger stressor with the potential to trigger much harsher cognitive appraisals depending on: a) our core beliefs; and b) how important it is to us to be in a relationship.

And the more value we place on being in a relationship, the more that relationship brings a sense of meaning or purpose or fulfillment to our lives, then the greater the loss we experience if the relationship ends. Because we’re not just losing the relationship ,our self-image takes a big hit and we’re losing self-esteem and self-worth and purpose and meaning.

And so if this is the case the negative cognitive triad is going to interact with the loss of the relationship in ways that lead to very negative cognitive appraisals: I’m worthless; I’m unlovable; my life has no meaning; if i care about someone they always end up hurting me; I’m never going to meet anyone like this again; I’m never going to be happy; I’m always going to be alone. And so it’s probably pretty clear how these sorts of cognitive appraisals could leave us feeling depressed.

But if we had a different set of core beliefs that weren’t so negative, and if being in a relationship wasn’t as important to us in terms of our self-esteem self-worth and meaning and purpose in our lives, then we’d make different sorts of cognitive appraisals about the end of the relationship that wouldn’t necessarily trigger depression. I’m really sad right now but it’s going to be okay. I’m lucky to have such good friends that care about me and will help me through it. I’m a good person with lots going for me and i know eventually the right person will come along.

Or maybe we lose our jobs. And again whether or not this is a kind of stressor that could lead us to become depressed will depend on how we appraise the situation, which will depend on our core beliefs. And it’ll depend on the importance we placed on having this job. If it’s a job we don’t care about that much and we can easily find a similar job and we can afford not to work for a while, sure nobody likes getting fired, and it’s a pain to have to find another job, but losing the job can be seen as just a temporary setback that isn’t that difficult to overcome, and isn’t necessarily going to damage our self-image or self-esteem or self-worth. And so it’s not the type of loss or stressor that tends to lead to depression.

But if this is our dream job and a lot of our self-esteem and self-worth is connected to our jobs or careers, and this job brings a sense of meaning and purpose and direction to our lives, and we’re really pessimistic about our abilities to find a similar job in the future, then losing our jobs is the type of loss that, if we have a predisposition to depression, could very likely lead us to become depressed.

So whether or not a negative life experience or stressor leads us to become depressed will depend on the subjective severity of that stressor, how significant was that stressor or loss to us based on our core beliefs and our values and what we find important in life, and how much we have invested in what we’ve lost. And it’ll depend on the cognitive appraisals we make about the situation.

And whether or not this loss triggers depression will depend on our levels of tolerance and on how resilient we are and how well we’re able to cope with the loss through things like resourcefulness and problem solving; and with the help of our social supports; and through our own internal resources such as our ability to regulate our emotions cope with stress and deal with and manage the consequences of the loss. And so if our levels of predisposition and vulnerability to depression plus the severity of the loss or stressor we’re facing outweighs our levels of tolerance and resiliency then we become depressed.

So what are the implications of this model in terms of treating and preventing depression and depression relapse? Well we can reduce how likely it is we become depressed by doing things that decrease our predispositions and vulnerabilities to depression and by doing things that increase our tolerances for stress and our resilience.

Let’s start with the negative cognitive triad because this is a part of the model where all of the predisposition roads lead and determines how we appraise the stressors that can lead to depression. Our core beliefs are long-standing and develop over the course of our lives and are resistant to change but that doesn’t mean we can’t change them. When we modify our core beliefs to make them less negative then we reduce our levels of predisposition to depression. And cognitive behavioral therapy can help us do this.

And cbt and mindfulness based therapies can also help us counter negative cognitive biases and change how we interpret and appraise life stressors and losses that can lead to depression, increase our tolerances for stress and loss, and make us more resilient, as can various strategies from positive psychology and research into happiness and well-being. And while we can’t go back and change our early childhood experiences therapy can help us work through issues from our childhoods that are contributing to a predisposition to depression.

Now what about biology? Neuroplasticity refers to our brain’s ability to physically alter its structure and form new neural pathways and connections and change how it responds to various stimuli throughout our lives. And we can do this, actually alter our brain’s biology with cbt and with mindfulness.

And then there are antidepressant medications. Now how do we know if we should be on an antidepressant? Well the short answer is we don’t we don’t really understand the biology of depression that well, and it’s possible that there are different subtypes of depression that we’re not able to differentiate right now, and that some who will respond to drug treatments better than others, some may be very hard to treat without medication, and some may respond better to psychotherapy than to medication.

Broadly speaking the more severe the symptoms of depression the greater the benefits of antidepressant medication compared with placebo. But that doesn’t mean that all severe depression needs to be treated with medication. And so if you have questions about treating your depression with medication you should consult your doctor or a psychiatrist.

So i think the key takeaway from this model is that there are lots of things that factor into depression and we have the ability to change all or almost all of them in some way and that any positive change we make in any of them is going to help reduce depression and reduce future vulnerability to depression. Or as Aaron Beck puts it, “any intervention that targets key predisposing precipitating or resilience factors can reduce risk or alleviate symptoms of depression.”

Beck AT, Bredemeier K. A Unified Model of Depression: Integrating Clinical, Cognitive, Biological, and Evolutionary Perspectives. Clinical Psychological Science. 2016;4(4):596-619. doi:10.1177/2167702616628523

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