Métodos de Clonaje

Mood disorders are a set of conditions ranging from major depressive episodes or disorder, dysthymic disorder, manic episodes, bipolar I & II disorders and cyclothymic disorder (American Psychiatric Association, 2000). Recently in DSM-5, other conditions such as mood disregulation disorder and pre-menstrual dysphoric disorder have been included within the broader group of mood disorders (American Psychiatric Association, 2013). The main symptoms of mood disorders are depressed mood, loss of interest in activities, severe weight/appetite loss/gain, insomnia, psychomotor agitation or retardation, fatigue, feelings of worthlessness or guilt, inability to concentrate and/or take decisions, and suicidal ideation. Variations in the combination and duration of symptoms determine the diagnosis of a specific mood disorder (American Psychiatric Association, 2000, 2013).

Evidence on the association between ED and mood disorders is mixed, though the majority of research suggests there is a high prevalence of depression across all ED (Preti et al., 2009). An early study by Herzog and colleagues in a clinical population found that depression was the most commonly diagnosed comorbid condition in both AN and BN (Herzog, Keller, Sacks, Yeh, & Lavori, 1992), and according to a recent literature review, mood disorders are reported in 24.1% to 90% of BN cases, and in 31% to 88.9% of AN cases (Godart et al., 2007). A clinical study of 322 ED patients diagnosed with AN-R, AN-BP, BN and BED found no differences in the prevalence of depression amongst the 4 groups (Fassino, Piero, Gramaglia, & Abbate-Daga, 2004). Similarly, a study of 2,436 ED patients (AN-R, AN-BP, BN, EDNOS) found no differences unipolar depression across ED categories (Blinder et al., 2006).

Other clinical studies have reported mood disorders to occur more frequently in binge/purge-types of ED (i.e. AN-BP, BN-P) than in those with restrictive-type of ED (i.e. AN-R)(Braun, Sunday, & Halmi, 1994; Fornari et al., 1992; Tozzi et al., 2005). The same finding has been replicated in general

population studies. Two large US surveys of adolescents and adults found high odds of mood disorders in individuals with BN and BED (Hudson et al., 2007; Swanson et al., 2011). The association of AN with mood disorders was non-significant in adolescents (Swanson et al., 2011). Adults with AN, on the other hand, had higher odds of having mood disorders (OR: 2.4, 95%CI: 1.2- 4.7) than their healthy counterparts, although lower than those of participants with BN (OR:7.8, 95%CI: 3.6-16.8) and BED (OR:3.1, 95%CI: 1.9-4.8) (Hudson et al., 2007). It has been hypothesised that the frequently observed association between binge/purge-type (as opposed to restricting types) of ED and mood disorders could be partially explained by the higher prevalence of depression in older individuals compared to adolescents, and therefore higher levels of mood disorders being detected in BN, which is more frequently documented in older individuals than AN-R.

Studies investigating the comorbidity between mood disorders and BED have been heterogeneous in nature and results, although the majority have documented increased levels of depression in individuals with BED. Some studies found higher levels of depression in obese than in non-obese patients with BED, whereas other did not. Others have reported that individuals with BN have higher levels of mood disorders than those with BED. Differences in instruments used to measure eating disorder and depressive symptoms, age and type (e.g. community vs. clinical) of populations sampled population have been deemed possible factors explaining these inter-studies variations (Araujo, Santos, & Nardi, 2010). In fact, the majority of these studies employed clinical samples with no controls; therefore it is possible that results are biased in favour of higher rates of depression than those that would typically be found in general population settings. Large general population surveys report contrasting findings. Some studies using adults and adolescent samples seem to confirm that BED is associated with mood disorders although to a lower extent than BN (Hudson et al., 2007; Kessler et al., 2013; Swanson et al., 2011), whereas others found the opposite in adolescents (A. E. Field et al., 2012).

There is increasing evidence that sub-threshold ED diagnoses and ED behaviours are also associated with mood disorders. Several large surveys have investigated the comorbidity between EDNOS and mood disorders both in adults (Hudson et al., 2007; Le Grange et al., 2012; McBride et al., 2012) and adolescents (A. E. Field et al., 2012; Le Grange et al., 2012; Swanson et al., 2011). One study found that between 27% and 41% of participants with different types of EDNOS (i.e sub-threshold AN, sub- threshold BED and EDNOS) reported mood disorders (Le Grange et al., 2012). Binge eating types of disordered eating have been found to be associated with mood disorders in both US and UK adult samples (Hudson et al., 2007; McBride et al., 2012). In the UK, restrictive eating behaviours were also associated with mood disorders (McBride et al., 2012).

Amongst adolescents, those with sub-threshold diagnoses have been found to have higher odds of reporting mood disorders than healthy participants (A. E. Field et al., 2012; Herpertz-Dahlmann et al., 2008; Swanson et al., 2011), and those with sub-threshold AN of having higher odds of having mood disorders than those with full AN (Le Grange et al., 2012). A smaller clinical study of 85 patients (aged 13-20) taking part in a family therapy trial found that EDNOS patients had higher rates of depression than BN ones (Schmidt et al., 2008).

Amongst sub-threshold diagnoses evidence exists of increased mood disorders in individuals exhibiting purging behaviours only (i.e. without bingeing). An Australian study by Wade on 1,083 female twins, found that women with purging type of EDNOS exhibited higher levels of life-time depression than healthy participants (Wade, 2007b). In a community sample of 111 women age 18-45 mood disorders occurred more frequently amongst women with purging disorder than in healthy ones although less frequently than in women with BN (Keel et al., 2005). In another longitudinal study of 2,890 Norwegian adolescents, those who purged only were found to have higher depressive symptoms than both healthy and other ED participants (Abebe et al., 2012)

Interim conclusions

Although some studies do not find differences in comorbidity with mood disorders across ED diagnoses (Blinder et al., 2006; Fassino et al., 2004), there is some indication that the former might be more prevalent in individuals exhibiting binge/purge type of ED such as BN (Tozzi et al., 2005). Mood disorders also appear to be prevalent in individuals with sub- threshold diagnoses and more often in those with binge/purge behaviours (A. E. Field et al., 2012; Hudson et al., 2007). Individuals with purging disorder have been found to have higher levels of comorbid mood disorders than healthy controls and restricting participants, but often not higher than those seen in individuals with BN (Keel et al., 2005). More general population studies are needed to investigate comorbidity of threshold and sub-threshold ED with mood disorders. Specific attention should be given to the study of comorbidity of mood disorders with BED and PD, as fewer studies have investigated them in general population settings and across various age groups.