Someone's brain with depression looks like and shows lower activity as well as reduced blood flow in areas that control mood and thinking, alongside of higher activity in areas that process stress.
The key areas of the brain that are affected when a person is depressed are the prefrontal cortex, hippocampus, amygdala and the nucleus accumbens.
The prefrontal cortex is the front area of the brain that handles focus, decision making and emotional control and it often shows low blood flow and reduced activity, which leads to feeling slow, unmotivated, or unable to concentrate.
The hippocampus is the center of the brain that manages memory and stress hormones and in chronic depression the hippocampus can physically shrink or lose gray matter volume because ongoing stress stops new neurons from growing.
The amygdala is the region of the brain that processes fear and emotional threats and in a depressed brain, the amygdala is often overactive and enlarged, which causes a constant reaction to negative emotions and stress.
And the nucleus accumbens is the brain's reward center and becomes less active in response to rewarding experiences, which also explains the lack of pleasure or motivation in depression also known as anhedonia.
The cellular and chemical changes that occur in the brain during depression include:
Neurotransmitters, where chemical messengers like glutamate, norepinephrine, serotonin and GABA misfire or become unbalanced, making communication between brain cells nosy and weak.
Synaptic connections, where severe stress causes the tiny branches also known as the synapses that connect the brain cells to pull back and detach.
And when treatment for the depression works effectively, these physical connections and chemical balances can also return to a healthy state.
The deepest form of depression is severe major depression that is accompanied by suicidal ideation, self harm, or even psychotic features, where your daily functioning also becomes completely debilitating.
Severe major depression is the worst stage of depression.
And while clinical depression is often viewed through levels of severity, which include (mild, moderate and severe) or progressive worsening phases rather than fixed "stages" of depression, the most dangerous and intense point of depression is marked by extreme functional impairment and crisis.
The key signs of severe depression include complete debilitation, severe emotional numbness or agony and crisis symptoms.
Complete debilitation in severe depression are where basic daily tasks, like showering, getting out of bed, eating or even working feel physically and even mentally impossible.
Severe emotional numbness or agony in severe depression involve intense feelings of worthlessness, crushing guilt and profound hopelessness taking over.
And crisis symptoms of severe depression involve emergence of thoughts of death, suicide, self harm, or in rare cases, psychotic features such as catatonia or delusions.
The common signs of severe depression are physical pain, severe isolation, extreme hopelessness, total loss of function and suicidal thoughts.
Suicidal thoughts include believing there is no escape from the agony, or that loved ones would be better off without you.
Total loss of function includes being unable to get out of bed, eat, bathe or do basic daily tasks.
Extreme hopelessness includes feeling completely empty, numb or convinced that life will never get better.
Severe isolation includes pulling away from all friends, family and support systems.
And physical pain includes experiencing any unexplained aches, severe fatigue, or extreme sleep and weight changes.