While the common signs of both depression and anxiety are shown in Table 1, as with stress these can vary. Diagnostically, the following criteria are used: 

Depression

One of two core symptoms must be present (persistent low mood; loss of pleasure in most activities) plus five out of nine additional symptoms present for most of the time on most days for at least two weeks (disturbed sleep, appetite and/or weight change, fatigue or loss of energy, agitation or slowed movements, poor concentration or indecisiveness, feelings of worthlessness or guilt, suicidal thoughts or acts).

Generalised anxiety disorder

An individual must have experienced at least six months’ excessive worry not relating to any particular circumstances that is causing distress or impairment, plus at least three of restlessness/nervousness, being easily fatigued, poor concentration, irritability, muscle tension and disturbed sleep.

There are, of course, many other serious mental health problems such schizophrenia, bipolar
disorder and personality disorders, but these are outside the scope of this module. 

Table 1: Distinguishing between stress, depression and anxiety

Stressed
Physical symptoms: Headaches, dizziness, tense or aching muscles, GI disturbances, raised heart rate
Emotional signs: Difficulty concentrating and making decisions, feeling overwhelmed, bein forgetful, constantly worrying
Behavioural changes: Irritability, sleeping too much or too little, appetite changes, avoiding people or places, drinking or smoking more

Depressed
Physical symptoms: Slow speech/movements, weight loss or gain, constipation, lack of energy, unexplained aches and pains, disturbed sleep
Emotional signs: Continuous low mood, feeling hopeless or helpless, low self-esteem, indecisiveness, anxiety, guilty or suicidal thoughts
Behavioural changes: Avoiding friends and social activities, neglecting hobbies and interests, difficulties at home and/or at work,

Anxious
Physical symptoms: Palpitations, dizziness, headaches, chest pain
Emotional signs: Inability to relax, feeling tense or nervous, worrying, tearfulness, insomnia
Behavioural changes: Appetite loss, not able to enjoy leisure time, self-neglect, struggling with relationships, reluctance to try new things.