By Dr. David Woo - January 9, 2020
It’s common for people who have an anxiety disorder, ADHD, post-traumatic stress disorder, or a traumatic brain injury to also be suffering from depression. Rates of depression among people with these conditions are higher than rates of depression among the general public.
When depression is diagnosed alongside another condition, it’s referred to as “comorbid.” For example, if a patient has been diagnosed with both anxiety and depression, he/she has comorbid anxiety and depression.
How often does someone with a non-depressive disorder also have depression? And why does this occur?
The Link between Anxiety and Depression
What Is Anxiety?
In the clinical sense, anxiety is more than simply feeling anxious or stressed. Stress and worry are healthy, natural responses to many normal situations people encounter. There is healthy stress, but there is unhealthy stress too. Stress becomes unhealthy when it begins to negatively affect your daily functioning. Patients with clinical anxiety experience anxious thoughts and emotions that may cause difficulty sleeping, eating, performing at work or school, or being social.(1)
Among patients diagnosed with anxiety, it is estimated that more than 50% have also had at least one depressive episode in their lifetime.(2,3) Studies have shown that patients diagnosed with anxiety are 7 to 62 times more likely than people not diagnosed with anxiety to develop depression within a year of being diagnosed.(4)
Scientists may have discovered a link between anxiety and depression, and it may be related to the way the brain works under stress. Stress and anxiety are regulated by specific structures in brain cells, called receptors. Certain receptors, when triggered by stress, are known to cause anxiety and depressive symptoms. A study published in Nature Neuroscience reveals that an increase in certain receptors associated with anxiety, called CRFR1, leads to an increase in the number of other receptors associated with depression, called 5-HT2R.(5,6)
The Link between Attention Deficit Hyperactivity Disorder (ADHD) and Depression
What Is ADHD?
ADHD is a behavioral disorder characterized by difficulty paying attention, hyperactivity, and/or difficulty controlling impulsive behavior. It affects 6.1% of American children and about 4% of American adults. There are three types of ADHD:(7,8,9)
- Inattentive ADHD describes patients who experience difficulty with paying attention, like absent-mindedness, being easily distracted, difficulty focusing to finish a task.
- Hyperactive ADHD refers to symptoms of hyperactivity or impulsivity, such as difficulty staying still, being quiet, or waiting.
- Combined type ADHD occurs when patients display symptoms of both inattentive and hyperactive ADHD.
Depression is one of the most common co-occurring disorders seen in patients diagnosed with ADHD. Experts estimate that up to 70% of individuals diagnosed with ADHD will suffer from depression at some point in their lives. Up to 30% of children diagnosed with ADHD are thought to have depression.(10)
ADHD and depression can be difficult to diagnose because the two conditions cause similar symptoms: Mood problems, lack of motivation, and inability to focus or concentrate. Depression can develop in people with ADHD when their condition has not been recognized and diagnosed early on. Children with ADHD can develop low self-esteem if constantly told that they are lazy, not smart, or not good enough to succeed. Moreover, children with hyperactive ADHD can be aggressive, while children with inattentive ADHD can seem withdrawn, which affects their ability to socialize and can lead to social exclusion.(11,12)
The Link between Post-Traumatic Stress Disorder (PTSD) and Depression
What Is PTSD?
PTSD is an anxiety disorder that can result from traumatic experiences, such as dangerous events or the unexpected loss of a loved one. Someone with PTSD may experience symptoms such as:
- Night terrors or flashbacks
- Avoidance of triggering thoughts or places
- Emotional outbursts
- Loss of memory about an event
- Affected mood, such as feelings of sadness, guilt, or loss of interest in activities a person used to enjoy
These symptoms impose significant difficulty or even inability to function in regular daily activities.(13)
Researchers state that 52% of individuals diagnosed with PTSD also suffer from depression.(14) Researchers have also found that people with PTSD are three to five times more likely to develop depression compared to people who do not have PTSD.(15)
PTSD and depression may occur together because trauma can also trigger depressive symptoms. Studies have shown that exposure to a traumatic event that occurred early on in life is a major risk factor for the development of depression.(16)
The Link between Traumatic Brain Injury (TBI) and Depression
What Is a Traumatic Brain Injury?
A TBI is a general term for an injury to the brain as a result of a traumatic event to the head. A common example of a TBI is a concussion. TBIs may occur from even mildly traumatic events, and causes may include everything from bumps on the head to skull fractures. Mild to moderate TBIs may cause symptoms including headaches, nausea, and cognitive disruptions. Severe TBIs may result in mental disability, coma, and even death.(17)
As much as 56% of people who suffer a traumatic brain injury show symptoms of depression just 10 weeks after their injury. Among individuals who suffer a mild-to-severe TBI, 53% will suffer depression, compared to 7% among people who have not suffered a TBI.(18)
Scientists believe that inflammation associated with TBI may contribute to the development of depression. Inflammation can occur for years following a TBI. Chronic inflammation is thought to be caused by certain proteins, called cytokines and chemokines. Scientists have found that following a TBI, levels of cytokines and chemokines increase. These proteins have been linked to increased rates of depression.(18,19)
Why Does Depression Occur Alongside Anxiety, ADHD, PTSD, or TBI So Often?
There is one important link that connects depression to other conditions like anxiety, ADHD, PTSD, and TBI—the frontal lobe of the brain. The frontal lobe is involved in numerous functions relating to mood, including self-awareness, personality, attention, memory, and moral and social reasoning.(20,21)
In the case of depression and anxiety, researchers believe that an imbalance in activity in the left and right frontal lobes causes these two conditions to occur at the same time. When the right lobe is overactive, it can lead to symptoms associated with both depression and anxiety, like withdrawing and being defensive.(22)
TMS May Treat Conditions Other Than Depression
In addition to depression, TMS has shown positive results in treating conditions like anxiety, PTSD, OCD, ADHD, and TBI.(23,24,25,26) To learn more about TMS and how it helps people with depression and other conditions, visit our website.
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6. Biological link between stress, anxiety, and depression identified. Science News. Published April 19, 2010. https://www.sciencedaily.com/releases/2010/04/100411143348.htm. Accessed December 17, 2019.
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8. What Is ADHD? Center for Disease Control and Protection. Updated January 26, 2021. https://www.cdc.gov/ncbddd/adhd/facts.html. Access May 4, 2022.
9. ADHD by the Numbers: Facts, Statistics, and You. Healthline. Updated July 23, 2018. https://www.healthline.com/health/adhd/facts-statistics-infographic. Accessed May 4, 2022.
10. Depression. CHADD National Resource Center. Publication Date Unavailable. https://chadd.org/about-adhd/depression/. Accessed December 17, 2019.
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13. Post-Traumatic Stress Disorder. National Institute of Mental Health. Updated May 2019.
https://www.nimh.nih.gov/health/topics/post-traumatic-stress-disorder-ptsd. Accessed May 4, 2022.
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17. Dixon K. J. Pathophysiology of Traumatic Brain Injury. Physical Medicine and Rehabilitation Clinics of North America. 2017;28(2), 215–225. https://pubmed.ncbi.nlm.nih.gov/28390509/. Accessed May 4, 2022.
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22. Nelson BD, Sarapas C, Robison-Andrew EJ, Altman SE, Campbell ML, and Shankman SA. Frontal brain asymmetry in depression with comorbid anxiety: A neuropsychological investigation. Journal of Abnormal Psychology. August 2012;121(3):579–591. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3710686/. Accessed January 02, 2020.
23. Cirillo P, Gold AK, Nardi AE, Ornelas AC, Nierenberg AA, Camprodon J, and Kinrys G. Transcranial magnetic stimulation in anxiety and trauma‐related disorders: A systematic review and meta‐analysis. Brain and Behavior. June 2019;9(6):e01284. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6576151/. Accessed December 17, 2019.
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