Not all persons with depressive states present the same symptoms, since the frequency and duration of symptoms varies depending on the type of depression that the person is going through.

• Feelings of sadness, loneliness or emptiness that last most of the day for several days
• Loss of interest or pleasure in activities that used to be nice
• Fatigue and chronic low energy
• Difficulty thinking clearly, concentration, make decisions or remember
• Feelings of being useless, guilt and powerlessness
• Feelings of irritability, frustration or anger that are disproportionate to the circumstances
• Restlessness and agitation
• Sleep disorders, including sleeping too much and too little (insomnia)
• The change of appetite, often leads to weight loss, although some people may have increased appetite and weight gain
• Recurrent thoughts of death or suicide, as well as suicide attempts or plans
• Aches and persistent pains, such as headaches or stomach upset

In some cases depression co-exists with mental disorders such as anxiety, posttraumatic stress, obsessive compulsive disorder, panic or phobia. Likewise, depression can be generated as a result of abuse, alcohol dependence or other substances, or as a result of medical conditions such as heart disease, cancer, diabetes, Alzheimer's or HIV/AIDS, among others.