While they have very similar symptoms, Brief Psychotic Disorder symptoms last at least 1 day but less than 1 month.

A manic episode consists of an abnormally and persistently elevated, expansive, or irritable mood and abnormally and persistently increased activity or energy lasting at least 1 week and present most of the day, nearly every day. A hypomanic episode consists of the same symptoms, but lasting at least 4 consecutive days.

The symptom pattern in Acute Stress Disorder must occur within a month of the traumatic event and resolve within that 1 month period.

Though individuals with Specific Phobias may experience panic attacks when confronted with the feared stimulus, they only occur in the context of the specific fear. Panic attacks for those with Panic Disorder are unexpected.

Although social isolation can be present in a variety of personality disorders, Schizoid differs from Schizotypal because of the perceptual distortions and marked eccentricity or oddness of Schizotypal Personality Disorder.

While they have very similar symptoms, Schizophreniform lasts more than 1 month but less than 6 months, while Schizophrenia symptoms must persists for at least 6 months.

For a diagnosis of Bipolar II, a person must meet the criteria for a current or past hypomanic episode AND the criteria for a current or past major depressive episode. However, for a diagnosis of Bipolar I, a person must meet the criteria for a manic episode. The manic episode may have been preceded by and may be followed by hypomanic or depressive episodes, but they are NOT required.

In Adjustment Disorders, the stressor can be of any severity rather than o the severity required for Acute Stress Disorder and PTSD. Adjustment Disorders can be diagnosed immediately and persist up to 6 months. PTSD can't be diagnosed until at least 1 month has passed.

Individuals with Specific Phobias may fear embarrassment or humiliation, but they do not generally fear negative evaluation.

BPD often co-occurs with depressive or bipolar disorders. If that happens, both can be diagnosed. To have BPD a person must have a documented pattern of behavior with an early onset and longstanding course. (Interpersonal issues are usually a clue)

A person with Delusional Disorder will not have markedly impaired functioning outside of the impact of their delusions. Moreover, delusional and psychotic disorders are characterized by a period of persistent psychotic symptoms. To diagnose Paranoid Personality Disorder the person must have disorder prior to developing psychotic symptoms have symptoms that persist regardless of psychotic symptoms (i.e. when they are in remission).

While some symptoms may overlap, Cyclothymic Disorder symptoms are long lasting (at least 2 years) and do not meet the criteria for a hypomanic or major depressive episode.

To be diagnosed with Depersonalization/Derealization, symptoms do not occur in the context of another dissociative disorder. So basically, they wouldn't have any other DID or PTSD symptoms. Just derealization and depersonalization.

Individuals with Social Anxiety have anticipatory anxiety about upcoming social situations and concerns about being evaluated, while individuals with GAD worry whether or not they are evaluated.

A person with OCD has true obsessions and compulsions. OCPD is more about rigidity.

A person with Schizoaffective Disorder will experience delusions and/or hallucinations or at least 2 weeks in the absence of a major mood episode.

Persistent Depressive Disorder is longer lasting, with symptoms for at least 2 years. The criteria for MDD may be continuously present. However, these symptoms can be slightly less acute but longer lasting.

Flashbacks in which the individual feels or acts as if the traumatic event was recurring, depersonalization, derealization.

In GAD, the worry is about forthcoming problems and it's the excessiveness of worry about future events that is not normal. In OCD the obsessions are inappropriate ideas that take the form of unwanted or intrusive thoughts, urges, or images.

Both are characterized by feelings of inadequacy, hypersensitivity to criticism, and a need for reassurance. They are likely to co-occur, despite that the primary focus for Avoidant PD is avoidance of humiliation and rejection, and the primary focus for Dependent PD is being taken care of.

A person with Schizotypal Personality Disorder must have been diagnosed with the disorder prior to having psychotic symptoms and will have symptoms that persist regardless of psychotic symptoms (i.e. even when they are in remission).

To be diagnosed with PDD, symptoms must be present in the final week before the onset of menses and store to improve within a few days after onset of menses and become minimal or absent in the week postmenses.

Reactive Attachment Disorder and Disinhibited Social Engagement Disorder.

Individuals with ADHD and ASD both have difficulties with inattention, social dysfunction, and have hard to manage behavior. Social difficulties in individuals with ADHD must be differentiated from the social disengagement, isolation, and indifference to facial and tonal communication seen in those with ASD.

The most useful feature for differentiation is the grandiosity of Narcissistic PD. Excessive pride in achievements, a relative lack of emotional display, and disdain for others' sensitivities help distinguish Narcissistic PD.