Clinical observations and epidemiological studies prove a vast overlap between Bipolar and Major Depressive Disorder. These observations are in line with Kraepelin’s view of
mood disorders and his attempt to bring all affective diseases under one rubric (Goodwin & Jamison, 2007). Thus the diagnosis between the various affective subtypes are not fast neither easy. For instance, bipolar disorder can be overlapping on cyclothymic disorder that could persist after the end of manic or depressive episodes. Likewise, evidence indicates that dysthymic disorder may precede major depressive disorder in a third of cases and, crossing from dysthymic disorder to hypomanic/manic episodes has also been described, suggesting that some forms of dysthymia are precursors of bipolar disorder. Moreover, one in four persons with major depressive disorder subsequently develops hypomanic/manic episodes and so should be reclassified as having bipolar disorder. There are many causes for the misdiagnosis of bipolar depression as unipolar depression: for instance patients’ lack of insight with regard to manic (especially hypomanic) symptoms (Goodwin & Jamison, 2007); in this regard is well known that depression not only impairs memory but also makes it more likely that memories will focus on past depressions. Thus, even if patients had previously some insight about manic symptoms, they often have difficulty recalling those symptoms clearly and accurately. Furthermore, during depression, mania or hypomania may be remembered simply as a good period and therefore patients do not report it spontaneously in the interview with the clinician (Benazzi Helmi, & Bland, 2002; Goodwin & Jamison, 2007). Moreover clinicians often don’t investigate about patient’s history from family or other significant and clinicians often focus on euphoric symptoms to diagnose mania, and they don’t account on dysphoria or irritability which are also symptoms of manic episode (Benazzi, & Akiskal, 2005; Perugi, Akiskal, Micheli, Toni, Madaro, 2001; Sato, Bottlender, Schroter, Moller, 2003). Rihmer and Kiss (2002) reported that patients with bipolar-II disorder are often misdiagnosed and then included as unipolar patients. Thus, the tendency to misdiagnose bipolar-II disorder
as unipolar depression may contribute to the apparently higher suicide rates in unipolar illness.
Many authors compared the symptoms of unipolar depression with those of bipolar depression, the result may be very helpful for psychotherapeutic and pharmacological treatment. The findings showed more symptoms of anxiety, somatic complaints (Beigel, & Murphy, 1971; Greenhouse, & Geisser, 1959) and psychomotor retardation (Goodwin & Jamison, 2007) in Major depressive Episode (MDE) of Unipolar Patients; while there are more symptoms of tension (Goodwin & Jamison, 2007; Vöhringer, & Perlis, 2016), mood lability (Brockington, Helzer, Hillier, & Francis, 1982; Hantouche, & Akiskal, 2005;), irritability (Benazzi, & Akiskal, 2005; Fava, & Rosenbaum, 1999), late insomnia (Goodwin & Jamison, 2007; Oral, & Vahip, 2004), psychotic features (Coryell, & Tsuang, 1985; Mitchell, 2001; Parker et al., 2000) and comorbid substance abuse (Judd et al., 2003; Marneros, 2004) in MDE of bipolar patients. Furthermore many authors assessed different depressive episodes between bipolar I and bipolar II patients. Bipolar II patients have more number of episodes, more rapid cycling and they spend more time in depression (Benazzi, & Akiskal, 2005; Goodwin & Jamison, 2007; Vieta, Gasto, Otero, Nieto, & Vallejo, 1997); conversely Bipolar I patients have more hospitalizations, irritability, and psychotic features (Goodwin & Jamison, 2007; Serretti & Olgiati, 2005; Vieta et al., 1997). Regarding the prevalence of suicide attempts, different findings have been reported. Some studies show greater suicidal behavior in bipolar II (Goldring, & Fieve, 1984; Rihmer, & Pestality, 1999), other studies suggest suicide attempts are the same in the two disorders (Coryell, Keller, Endicott, Andreasen, Clayton, & Hirschfeld, 1989; Vieta et al., 1997).
Considering the assessment phase, mixed depression have a significant clinical relevance in mood disorders and may occur in both bipolar and unipolar disorder (Akiskal, Benazzi, Perugi, & Rihmer, 2005; Benazzi, Helmi & Bland, 2002).
Nevertheless, there are limits of information of mixed depression and therefore it is already an underestimation of the consequences, which could result in misdiagnosis and inappropriate/wrong treatment, often with very dangerous outcomes both for the course of the illness and for the suffering of patients (Akiskal et al., 2005; Bocquier et al., 2013). In particular, treatment with antidepressant drugs in agitated depression (AD) could worsen the excitatory symptoms resulting in the failure to relieve the patient’s pain (Akiskal et al., 2005; Koukopoulos, & Koukopoulos, 1999; Vázquez, Tondo, Undurraga, & Baldessarini, 2013). Indeed, it has been reported that antidepressants monotherapy in AD might increase psychomotor agitation. Moreover, concerns have been reported about the possibility that the antidepressant administration in the agitated depression could increase the risk of suicide (Akiskal et al., 2005; Baldessarini et al., 2006a; Koukopoulos, & Koukopoulos, 1999; Vázquez, Tondo, Undurraga, & Baldessarini, 2013).
These observations suggest that much of the unipolar spectrum might be “soft bipolar”. The clinical significance of these considerations are of clinical relevance especially as far as it is concerned the switches in polarity and the resulting clinical and pharmacological treatment of various types of depression (Goodwin & Jamison, 2007). Irritability may be a good marker of depression with mixed features, a view consistent with that of others who have found high rates of irritability and anger attacks associated with these states (Akiskal, & Benazzi, 2003; Koukopoulos et al., 2007; Sani et al., 2014). According to several studies, there is a significant greater proportion of Agitated Depression in Bipolar Disorder than in MDD (Benazzi, 2004a; Benazzi et al., 2004; Koukopoulos et al., 2007; Takeshima, & Oka, 2013).
This awareness can help the clinician to avoid the all-too-common misdiagnosis of agitated depression and other depressive/manic symptoms, a mistake that can lead to the almost always frustrating treatment decision and the administering an antidepressant in
the absence of a mood stabilizer (Baldessarini, Tondo, Davis, Pompili, Goodwin, & Hennen, 2006b; Baldessarini et al., 2013).
Anyway, the data suggest greatly elevated suicide rates in both unipolar and bipolar disorders in comparison with other psychiatric diseases (Sharma, & Markar, 1994; Harris, & Barraclough, 1997).
The most prudent approach is perhaps to give clinicians the opportunity to maximize the assessment phase of each case. The result of a good assessment and therefore of a correct diagnosis is the possibility of treating the individual in an effective way. The diagnosis of a type of depression cannot be accomplished by a checklist: The DSM-5 diagnostic criteria for major depressive episode provide only a general guide. Only after an in depth phenomenological approach can a clinician ascertain diagnosis of a specific affective episode and choose the most appropriate treatment.