Shimon sometimes experiences periods of major depression. At other times, he is extremely talkative and active, appears to be in a euphoric mood, goes days without sleeping, and reports that his thoughts are racing. The most likely diagnosis of Shimon's condition is:

Bipolar disorder.

Explanation:

In psychology and psychopathology and according to the DSM-V the bipolar disorder is a mental disorder that causes shifts in mood and activity levels in a clear pattern that is described in the next paragraph:

When a person has this disorder, the person can have extreme changes like going from extremely energized behavior followed by episodes where they feel really "down", sad and depressed.

In this example, Shimon experiences periods of major depression but then he has some periods where he is extremely talkative and active and in a euphoric mood. We can see that Shimon is having extreme changes from extremely energized behavior followed by episodes where he feels sad. Thus, the most likely diagnosis for him is Bipolar disorder.

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explanation:

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