Depression Signs & Symptoms

Depression is not a single condition, but a spectrum of disorders. Each type has its own symptoms, underlying causes, and treatment methods. Common types of depression include: 

• Major depression (MDD), otherwise known as clinical depression or unipolar depression 
• Persistent depressive disorder, or dysthymia 
• Seasonal affective disorder (SAD)
• Postpartum depression
• Bipolar depression   

What Are The Risk Factors of Depression? 

Regardless  of age, race, income, culture, or education, depression can affect anyone at any time. However, certain risk factors can increase the likelihood of depression, including genetic predispositions, physical brain differences, and environmental influences. 

Genetic Factors

Depression often runs in families, which is why genetics are taken into consideration when diagnosing someone with the condition. If someone has a parent, sibling, or another first-degree relative with depression, their risk of inheriting it increases by 1.5 to 3 times. While this doesn’t mean that they’re destined to develop depression, it does show how inherited traits can influence vulnerability. 

Our genes control protein production, which affects how the brain manages mood and stress. Below are some gene variations that have been linked to depression: 

• 5-HTTLPR, which helps regulate serotonin, a chemical responsible for balancing mood
• COMT, which affects how the brain process dopamine, a chemical tied to motivation and feelings of reward
• BDNF, which supports brain cell growth and repair. This gene helps maintain emotional stability. 

Researchers have also found that abnormal methylation of genes like BDNF and SLC6A4 can impair the brain’s ability to adapt and respond to new experiences. This disruption could potentially make someone more sensitive to stress and more likely to develop depression.   

Physical Factors

Serotonin theory is a popular concept that has been used for decades to explain the cause of depression. It suggests that low serotonin levels are the main culprit; however, there is very little evidence to support this idea. Studies that artificially lower serotonin levels in healthy people have failed to induce depression, which has raised further doubts about the theory’s validity. 

Antidepressants like selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed based on this idea, but they may not work by correcting a serotonin imbalance. Instead, they might numb emotional responses or through placebo effects. While the theory has been debunked, there are still structural and functional changes in the brain that could contribute to depression, including: 

• Monoamine deficiency, which involves low levels of serotonin, norepinephrine, and dopamine
• Imbalances in glutamate and GABA, which regulate brain activity and emotional processing
• Mitochondrial dysfunction, which can cause reduced energy production and damage to brain cells 

Environmental Factors

The environment we live in can also contribute to the risk of developing depression. Environmental influences can affect brain development, stress responses, and emotional health. Research has found the following: 

• Air pollution (e.g., diesel emissions and fine particulate matter) can cause brain inflammation and cognitive challenges
• Urban noise from traffic or construction contributes to chronic stress and sleep disturbances
• Childhood trauma like emotional or sexual abuse disrupts brain development and increases vulnerability to mood disorders
• Chronic stress causes lasting changes in brain regions that are involved in memory, emotional regulation, and stress response
• Early attachment issues like caregiver loss or insecure attachment increase sensitivity to loss and negative emotions