Depressive Disorders—Is It Time to Endorse Different Pathophysiologies? Irina A
Total Page:16
File Type:pdf, Size:1020Kb
Psychoneuroendocrinology (2006) 31, 1–15 www.elsevier.com/locate/psyneuen REVIEW Depressive disorders—is it time to endorse different pathophysiologies? Irina A. Antonijevic* Department of Psychiatry, University Medicine, University of Berlin, Charite´, Germany Received 3 October 2004; received in revised form 15 February 2005; accepted 2 April 2005 KEYWORDS Summary Enhanced activity of the hypothalamic-pituitary-adrenal (HPA) axis, Major depression; involving elevated secretion of corticotropin-releasing hormone (CRH), is considered HPA axis; a key neurobiological alteration in major depression. Enhanced CRH secretion is also Sleep EEG; believed to contribute to the typical sleep alterations and the clinical presentation of Serotonin; major depression. Cytokines; While it is acknowledged that HPA overdrive and hypernoradrenergic function is Atypical features associated with melancholic depression, there is growing evidence that hypoactivity of the HPA axis and afferent noradrenergic pathways is present in patients with atypical features of depression. The clinical relevance of such a differentiation is highlighted by findings which suggest distinct responses to pharmacological treatments. Moreover, it has been reported that female patients respond better to selective serotonin re-uptake inhibitors (SSRI) than tricyclic antidepressants. Interestingly, the female predominance among patients with depression seems to be restricted to the atypical subtype. Besides HPA axis activity, distinct alterations of the serotonergic system may also play a critical role for the melancholic and atypical phenotypes, namely a reduced restrained via 5-HT1A autoreceptors in the former and primarily reduced serotonin synthesis in the latter. Moreover, there is evidence for an immune activation in patients with depression, the extent and duration of which may be distinguishable for the melancholic and the atypical subtype. In this regard, lessons can be learned from depressive symptoms in patients with autoimmune disease, associated with different alterations of the HPA axis, and in patients undergoing cytokine therapy. In conclusion, the available data today suggest that clinically relevant differences in the underlying pathophysiology in patients with depression exist. The identifi- cation of distinct endophenotypes for major depression will not only improve our understanding of the disease, but will also contribute to more specific treatment strategies. Q 2005 Elsevier Ltd. All rights reserved. 1. Introduction * Address. Lundbeck Research USA, 170 Williams Drive, Ramsey, NJ 07446, USA. Tel.: C1 201 350 0546; fax: C1 201 There is growing evidence that depressive disorders 818 1011. encompass a group of disorders, which differ with E-mail address: [email protected]. 0306-4530/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.psyneuen.2005.04.004 2 I.A. Antonijevic regard to hypothalamic–pituitary adrenal (HPA) axis respond more favourably to one rather than another activity, immune functions and the treatment antidepressant medication (Quitkin et al., 1993; response (Kornstein et al., 2000a; Gold and Chrou- Kornstein et al., 2000a; Stewart et al., 2002; Joyce sos, 2002; Murck, 2003; Murck et al., 2005). As early et al., 2004; Murck et al., 2005). This strategy can, as 1992, Chrousos and Gold put forward the in turn, contribute to our understanding of the hypothesis that sustained stress system dysfunc- underlying pathophysiology of subtypes of tion, characterised by either hyper- or hypoactivity depression. Such knowledge may be particularly of the HPA axis, play a role for various pathophy- useful when exploring phenotype–genotype siologic states, including a range of psychiatric, relationships. Though most publications today endocrine and inflammatory diseases (Chrousos and distinguish primarily the melancholic and atypical Gold, 1992). The HPA axis, in turn, plays a critical subtype, it is likely that the identification of further role for sleep regulation, which is distinctly endophenotypes will be possible in the future. disturbed in patients with typical symptoms of The present review summarises recent findings major depression (Kupfer, 1995; Steiger, 2002). on differences with regard to sleep-endocrine and One effort to clinically define a subtype of immunological alterations among patients with depression with a possibly distinct pathophysiology depression. Based on the model proposed by Gold and response to treatment is reflected by the and Chrousos (Gold and Chrousos, 2002), recent renewed discussion about the concept of atypical data on altered regulation of sleep, immune and depression (Quitkin et al., 1993; Posternak and serotonin functions are also integrated. Zimmerman, 2002; Parker et al., 2002; Angst et al., 2002; Benazzi, 2003; Murck, 2003). Though the debate regarding the best clinical criteria for atypical depression continues, the available data 2. HPA axis activity in depressive suggest that the neuroendocrine pathophysiology is disorders different, and even opposite, to that observed in patients with melancholic depression (Chrousos and Many studies have shown that a major depressive Gold, 1992; Gold and Chrousos, 2002; Murck, 2003). episode is characterised by typical neuroendocrine Another interesting field of research focuses on and sleep-EEG alterations. Overactivity of the HPA the role of immune activation for depressive axis, a key neuroendocrine alteration observed in disorders (for review see Licinio and Wong (1999), patients suffering from an acute major depressive Leonard (2001), Anisman and Merali (2002)). episode, is assumed to reflect an elevation of Evidence for an association includes data showing hypothalamic corticotropin-releasing hormone a high incidence of depressive symptoms (CRH) and vasopressin secretion (Gold and Chrousos, in some patients with activation of the inflamma- 1985; Roy et al., 1987; Nemeroff, 1988; Kupfer et al., tory response system. The latter includes in 1990; Lauer et al., 1991; Steiger et al., 1994; Buysse particular patients with cancer, infectious and et al., 1997; Holsboer, 1999; Antonijevic et al., autoimmune diseases (Garland and Zis, 1991; 2000b; Steiger, 2002). Enhanced secretion of CRH is Fassbender et al., 1998; Raison and Miller, considered to play an important role for behavioral 2001; Musselman et al., 2001b; Raison and Miller, symptoms typically associated with major 2003; Musselman et al., 2003; Feinstein, 2004). depression, namely enhanced anxiety, lost respon- Moreover, cytokine therapies, used for treatment siveness to the environment, a diurnal variation with of hepatitis C and cancer, have been repeatedly depressed mood at its worst in the morning, disturbed associated with an enhanced incidence of depress- sleep continuity, psychomotor alterations, ive symptoms (Bonaccorso et al., 2001; Musselman decreased appetite and libido as well as cognitive et al., 2001b; Capuron et al., 2002; Schaefer et al., impairment (Gold and Chrousos, 1985, 2002; Hols- 2003; Capuron et al., 2003a). boer, 1999). The effects of centrally released CRH are A better understanding of the differences in the thought to be mediated by CRH-R1 and R2 receptors underlying pathophysiology is critical for a classifi- in limbic areas such as the hippocampus and the cation of patients based on one hand on the clinical amygdala as well as afferent neurons in the locus presentation and on the other hand on the (neuro-) coeruleus and the dorsal raphe (Holsboer, 1999; biological profile. Ultimately, the identification of Roozendaal et al., 2002; Gold and Chrousos, 2002; endophenotypes for depression will help to Bale and Vale, 2003; Thomas et al., 2003). Seroto- choose the most appropriate treatment for a nergic neurons in the dorsal raphe nucleus, as well given patient (Hasler et al., 2004). Thus, over the as noradrenergic neurons in the brainstem and last years, several publications have suggested the locus coeruleus are important afferents for that subgroups of patients with depression may the regulation of hypothalamic CRH secretion Different pathophysiologies of major depression 3 (Cunningham et al., 1990; Vertes, 1991; Valentino density (Kupfer et al., 1990; Lauer et al., 1991; et al., 1993; Calogero, 1995; Dayas et al., 2001). Steiger et al., 1994; Buysse et al., 1997; Antoni- Moreover, a forward circuit between hypothalamic jevic et al., 2000b). Animal and human studies CRH neurons and noradrenergic neurons of the locus support a critical involvement of central CRH coeruleus, which is involved in the stress response, secretion in these sleep alterations (Ehlers et al., has been described (Valentino et al., 1992, 1993). 1986, 1997; Holsboer et al., 1988; Opp, 1995; Similarly, a circuit exists between brainstem and Chang and Opp, 2001; Steiger, 2002). Thus, CRH dorsal raphe nuclei and the amygdala complex (Imai disturbs sleep continuity, promotes EEG activity in et al., 1986; Vertes, 1991; Van Bockstaele et al., the higher frequency range and reduces slow wave 1998; Linthorst et al., 2002; Commons et al., 2003). sleep (Ehlers et al., 1986, 1997; Holsboer et al., As projections from the amygdala can stimulate the 1988; Opp, 1995; Chang and Opp, 2001; Steiger, HPA axis (Weidenfeld et al., 2002), a vicious circle 2002). Opposite effects have been noted for may sustain enhanced CRH secretion, hyperactivity hypothalamic growth hormone-releasing hormone of the amygdala and noradrenergic system in patients (GHRH), which improves sleep continuity, and with major depression (Roy et