Table 2 Validity of CRDC criteria for pure and mixed bipolar depression and bipolar spectrum disorder

Pure depression

Psychomotor slowing along with depressive mood

Anhedonia

Hyperphagia, hypersomnia

Decreasing libido

Loss of concentration

Usually bipolar, alternating with mania/hypomania/mixed states (Goodwin and Manic–depressive 2007)

Associated with BP and MDD to lesser degree (Goodwin and Manic–depressive 2007)

Little responsive to antidepressants, unlike MDD, based on placebo–controlled studies (Goodwin and Manic–depressive 2007; McGirr et al. 2016)

Associated with HPA axis activation and hippocampal and prefrontal cortex atrophy (Manji et al. 2001)

Mixed depression type I

Psychomotor activation along with dysphoric mood (Koukopoulos et al. 2007, 2005)

Marked inner tension (Koukopoulos et al. 2007, 2005)

Marked mood reactivity, rage (Koukopoulos et al. 2007, 2005)

Equally bipolar and unipolar, with recurrent mixed episodes (Koukopoulos et al. 2007, 2005)

Associated with BP (Sani et al. 2014a, b)

Little responsive to antidepressants, more responsive to antipsychotics (Sani et al. 2014a, b)

Unknown

Mixed depression type II

Psychomotor activation along with dysphoric mood

Three or more manic symptoms, similar to the DSM–IV approach, along with severe depression, but without any duration criterion (Angst et al. 2011)

Irritable mood, flight of ideas, hypersexuality, brief duration

Equally bipolar and unipolar, with recurrent mixed episodes (Angst et al. 2011)

Associated with BP (Angst et al. 2011)

Little responsive to antidepressants, more responsive to antipsychotics (Angst et al. 2011), (Benabarre et al. 2001), (Pae et al. 2012), (Patkar et al. 2012)

Unknown

Bipolar spectrum depression

Psychomotor activation or slowing, with dysphoric mood

Severe recurrent depression does not meet classic DSM–III or IV criteria for bipolar disorders type I or type II, nor the classic definition of major depressive disorder (Ghaemi et al. 2002)

Unipolar, with manic symptoms often but not always present (Angst et al. 2018)

Highly recurrent (Angst 2007)

History of rapid cycling (Angst 2007)

Associated with BP (Angst et al. 2018)

Potentially less responsive to antidepressants, more responsive to antipsychotics or lithium/anticonvulsants (Ghaemi et al. 2002)

Frequent presence of antidepressant switch (Ghaemi et al. 2002)

Unknown