Mood changes may be a constitutive feature of several psychiatric disorders and a broad classification based on the nature of the disorder (sadness or elation) can be made into depressive and manic mood changes, each presenting with distinct clinical features [1] [2]:

• Depressive disorders - Numerous subtypes have been described in literature - major depressive disorder, persistent depressive disorder, substance or medication induced, depression occurring as a result of another disease, premenstrual dysphoric disorder and unspecified forms [3] [4]. The presence of irritable or sad mood that substantially influences everyday life of affected individuals due to somatic and cognitive disturbances is a common finding in all of them, but their distinction can be made according to the duration, onset or the underlying etiology [2]. For example, major depressive disorder is diagnosed when mood changes last for at least two weeks, while persistent depression is suspected if symptoms last for two years in adults and one year in children [2]. Moreover, patients may suffer from psychotic, melancholic or catatonic episodes that can mislead the physician from depression as the underlying disorder.
• Mania and hypomania - Abnormally irritable and expansive mood present for one week accompanied by symptoms such as elevated self-esteem, decreased need for sleep, psychomotor agitation, racing thoughts, increased goal-directed activity and a propensity for distraction by irrelevant or unimportant stimuli are hallmarks of a manic episode [2] [5]. A fast rate of speech, verbosity, accelerated mental and physical activity, and personal belief that he/she is at an excellent mental state is often encountered, which can be dangerous or even life-threatening. A hypomanic state is described as a milder form of mania, lasting at least four days and presenting with less severe clinical symptoms than that observed in manic patients [5].
• Bipolar disorders - When manic episodes, depression, and/or hypomania are all seen in one individual, the diagnosis of a bipolar disorder should be suspected. Like in depressive disorders, several clinical types are recognized - type I, type II, drug-induced, etc. [1], while cyclothymia denotes a less severe form.

The diagnosis of a mood disorder can be quite challenging, having in mind the diverse clinical presentation and its variable appearance in patients. In addition, concomitant presence of anxiety disorders (social phobias, obsessive-compulsive disorders, or even panic attacks) may be noted, creating an even bigger issue to discern between the disorders [5]. For this reason, physicians must bear in mind that a long and carefully obtained patient history is the essential component during workup, as the majority of symptoms may not be evident during the hospital visit, but more importantly, because the diagnosis is made almost solely on clinical criteria [2] [5]. Not all patients will be able to describe typical changes seen in mood disorders, and some will not even admit that anything extraordinary is happening, which is why parents, close friends or even relatives can be interviewed as well. Apart from determining symptoms related to mood changes, physicians must inquire about recent use of drugs or substances that can induce such changes [3] [4], but also exclude some organic diseases that may mimic depression [5]. Thyroid hormone levels should be measured to exclude hypothyroidism, while folate, B12 and a complete blood count are recommended in the diagnostic workup as well [5].

1. Marvel CL, Paradiso S. Cognitive and neurological impairment in mood disorders. Psychiatr Clin North Am. 2004;27(1):19-viii.
2. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. Fifth Edition. Arlington, VA: American Psychiatric Publishing; 2013.
3. Quello SB, Brady KT, Sonne SC. Mood Disorders and Substance Use Disorder: A Complex Comorbidity. Science & Practice Perspectives. 2005;3(1):13-21.
4. Tolliver BK, Anton RF. Assessment and treatment of mood disorders in the context of substance abuse. Dialogues Clin Neurosci. 2015;17(2):181-190.
5. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J; 2011.