"This large nationwide registry linkage study confirms that the clinical picture in CFS/ME [chronic fatigue syndrome / myalgic encephalomyelitis] is complex."
That sentence, taken from the paper by Inger Bakken and colleagues  (open-access available here), is perhaps the under-statement of the year as authors sought to "describe comorbidities diagnosed in primary care in children diagnosed with CFS/ME in specialist health care" and "describe the timing of the diagnoses from primary care in relation to the timing of the CFS/ME diagnosis."
I grow tired of saying this but yet again, one of those very useful Scandinavian population registries was the starting point for the study - this time based in Norway - as some 1600 children diagnosed with CFS/ME were identified. Their data were compared against nearly 5000 children diagnosed with type 1 diabetes (T1DM) and a little over 1.3 million control - general child population - children. You could say that this was an adequately powered study.
A couple of important points were identified from the analysis of patient records. First: "Among children with CFS/ME, the most frequently observed primary care diagnosis was “weakness / general tiredness”." This is probably not unexpected given the nature of CFS/ME. Despite such weakness/general tiredness being initially identified in the vast majority of those with CFS/ME, sleep disturbances were also found more commonly among this group compared to other participants. Rather interestingly, asthma was also reported to be more common in the CFS/ME group than either of the control groups potentially reinforcing a role for atopy in the course/onset of at least some CFS/ME .
Next: "we found higher frequencies of depression and anxiety in the CFS/ME group." This is an important point that one has to be slightly careful with in terms of the introduction of psychological/psychiatric elements to a diagnosis of CFS/ME. I'll come back to this shortly.
Next: "Elevated frequencies of all diagnoses related to infection were observed in the CFS/ME group. In particular, infectious mononucleosis was far more frequent in this group (17.2 %) than in the control groups (T1DM: 3.7 %, general child population: 2.9 %). Influenza, acute tonsillitis, “strep throat”, and pneumonia were also more frequent in the CFS/ME group." Minus any sweeping generalisations, the suggestion that an infection illness might be part and parcel of at least some cases of CFS/ME is potentially borne out by this data. Infectious mononucleosis a.k.a glandular fever as a 'trigger' for CFS/ME is not unknown to the research  and other literature for example.
Finally: "The time span from the first primary care diagnosis of weakness / general tiredness to the specialist health care diagnosis of CFS/ME was 1 year or longer for 47.8 %." Whilst everyone would love to see a timely diagnosis of CFS/ME made, particularly when it comes to children, this data kinda suggest that diagnosis in Norway can still a long and drawn out process. Yes, I understand that many of the numerous diagnostic criteria used to diagnose CFS/ME rely on symptoms being present for an extended period of time but this does little to aid the child and their family and the important effects of such symptoms on things like schooling and other important facets of childhood.
The Bakken findings provide an important research snapshot of CFS/ME in children. The themes of (i) infection being potentially important to quite a few cases and (ii) the quite long time lag between primary care (i.e. General Practitioner, GP) diagnosis of weakness / general tiredness and specialist diagnosis of CFS/ME are important ones that research and practice can/should perhaps learn some lessons from.
Insofar as the observation of depression and/or anxiety being more frequently present in cases of CFS/ME, the authors make reference to the paper by Winger and colleagues  (see this post for more information). Winger et al reported that depressive symptoms in their group did not seemingly link/explain the reduction of health-related quality of life scores they reported for their cohort of adolescents with CFS. Taken together with the Bakken results, the implication is that whilst more commonly reported in CFS/ME, depression (and anxiety) issues are important to cases. They cannot however at this point be described as anything more than comorbid. I say this because, unfortunately, there are still opinions out there that might see depression, anxiety and other psychiatric manifestations as 'causative' of CFS/ME rather than, as I see it, being a symptom stemming from the effects of CFS/ME. If you are bed-bound, not able to go to school, not able to socialise properly and not able to do all the things your peers are doing, it is highly likely that your psychology will eventually be affected to some degree.
"The long time spans observed from the first diagnosis of weakness / general tiredness in primary care to a specialist health care diagnosis of CFS/ME might indicate that the treatment of these patients is sometimes not optimal." I also struggle to disagree with that sentence.
 Bakken IJ. et al. Comorbidities treated in primary care in children with chronic fatigue syndrome / myalgic encephalomyelitis: A nationwide registry linkage study from Norway. BMC Fam Pract. 2016 Sep 2;17(1):128.
 Yang TY. et al. Increased Risk of Chronic Fatigue Syndrome Following Atopy: A Population-Based Study. Medicine (Baltimore). 2015 Jul;94(29):e1211.
 Winger A. et al. Health related quality of life in adolescents with chronic fatigue syndrome: a cross-sectional study. Health Qual Life Outcomes. 2015 Jul 3;13:96.
Bakken IJ, Tveito K, Aaberg KM, Ghaderi S, Gunnes N, Trogstad L, Magnus P, Stoltenberg C, & Håberg SE (2016). Comorbidities treated in primary care in children with chronic fatigue syndrome / myalgic encephalomyelitis: A nationwide registry linkage study from Norway. BMC family practice, 17 (1) PMID: 27590471