Associated disorders
A single manic episode, in the absence of secondary causes, (i.e., substance use disorders, pharmacologics, or general medical conditions) is often sufficient to diagnose bipolar I disorder. Hypomania may be indicative of bipolar II disorder. Manic episodes are often complicated by delusions and/or hallucinations; and if the psychotic features persist for a duration significantly longer than the episode of typical mania (two weeks or more), a diagnosis of schizoaffective disorder is more appropriate. Certain obsessive-compulsive spectrum disorders as well as impulse control disorders share the suffix "-mania," namely, kleptomania, pyromania, and trichotillomania. Despite the unfortunate association implied by the name, however, no connection exists between mania or bipolar disorder and these disorders. Furthermore, evidence indicates a B12 deficiency can also cause symptoms characteristic of mania and psychosis.Hyperthyroidism can produce similar symptoms to those of mania, such as agitation, elevated mood, increased energy, hyperactivity, sleep disturbances and sometimes, especially in severe cases, psychosis.
Diagnosis
The following PIE principles were in place for the "not yet diagnosed nervous" (NYDN) cases:

Proximity – treat the casualties close to the front and within sound of the fighting. Immediacy – treat them without delay and not wait until the wounded were all dealt with. Expectancy – ensure that everyone had the expectation of their return to the front after a rest and replenishment.United States medical officer Thomas W. Salmon is often quoted as the originator of these PIE principles. However, his real strength came from going to Europe and learning from the Allies and then instituting the lessons. By the end of the war, Salmon had set up a complete system of units and procedures that was then the "worlds best practice". After the war, he maintained his efforts in educating society and the military. He was awarded the Distinguished Service Medal for his contributions.Effectiveness of the PIE approach has not been confirmed by studies of CSR, and there is some evidence that it is not effective in preventing PTSD.US services now use the more recently developed BICEPS principles:

Brevity
Immediacy
Centrality or contact
Expectancy
Proximity
Simplicity

Between the wars
The British government produced a Report of the War Office Committee of Inquiry into "Shell-Shock", which was published in 1922.