This clinical sample of 707 outpatients was enriched with children whose parents scored them ≥ 12 on the GBI-S10M (selecting for those with elevated symptoms of mania) at their first clinic visit. The majority (n = 589, 76.2%) had ADHD and a substantial proportion (n = 162, 22.9%) had BPSD (diagnosed with a requirement for episodes), with comorbid overlap of 16.5% (n = 117), slightly less than would be expected from multiplying the prevalence of the two disorders in this sample (17.5%, n~124). The failure to find greater comorbidity is relevant to a current controversy about the relationship of the two disorders. Some (15
), but not all (12
) literature claims greater than chance development of BPSD in the presence of ADHD. The difference of our findings from those of some other authors may be partially accounted for by definitions of BPSD and our careful diagnostic sorting of symptoms as described in the methods section. One might expect that the high proportion of shared symptoms would result in greater than chance overlap (40
). Indeed, if one automatically counts such symptoms as hyperactivity and impaired attention towards both disorders without noting association with mood episodes, and especially if one does not require episodicity for BPSD, it may artificially inflate the comorbidity rate. The differences in the way those symptoms are inquired, as illustrated in , can make a critical difference in assignment to diagnosis. On the other hand, the reconciliation of these divergent findings may rest in the difference between a clinical sample and population rates (41
). It seems that the increased risk of bipolar disorder reported in ADHD clinical samples, 10-fold or greater than the population base rate, may actually be the risk of being in a child mental health clinic population rather than being specific to ADHD.
Of the four hypotheses, two were supported (Hypothesis #3: function more impaired in the comorbid group by CGAS ratings; Hypothesis #4: number of other comorbid diagnoses greater in the comorbid ADHD + BPSD). One (Hypothesis #2: more severe symptoms in the comorbid group) was partially supported, and one (Hypothesis#1: earlier age of onset in the comorbid group) clearly failed.
However, concerning Hypothesis #4, the increment of additional diagnoses appeared greater for adding ADHD to BPSD than the reverse. Children with ADHD alone, compared to those with BPSD alone, had more than twice the rate of two or more other diagnoses (46% vs. 22%, both significantly less than the comorbid group, 71%). It appears that at this age, ADHD carries more comorbidity than BPSD. On the other hand, the need for hospitalization is carried by BPSD (22% vs. 5%), and addition of ADHD does not increase the rate of hospitalization.
The failure to find earlier onset of BPSD in the comorbid group is at odds with other reports (2
). We are at a loss to explain this difference. It may have resulted from the method of ascertainment; the others started with children with diagnosed BPSD, whereas we started with and undiagnosed sample with elevated symptoms of mania (and a few without such elevation). Another difference might be the age of the sample. For example, Masi et al (2
) reported age 8 onset of BPSD for the comorbid group and age 11 onset for the BPSD-alone group. Because our sample was age 6–12, we may have sampled too young to capture most of those for whom comorbidity or not would make a difference in onset age. This possibility is partially supported by the fact that those with BPSD without ADHD averaged a year older (p = 0.01) than the other diagnostic groupings at their first visit to the LAMS site clinic (an inclusion criterion was that this was the first visit to the respective clinic). Further, the BPSD + ADHD group first came to clinical attention at any clinic 1.3 years younger than the BPSD-alone group. Thus it appears that concurrent ADHD may bring the comorbid group to clinical attention a year or so sooner even if the age of onset is not different. This would be consistent with impairment being more severe in the comorbid group, which may precipitate clinical attention at a younger age. However, the age difference for first clinical presentation anywhere failed to reach significance by a conservative statistical test that allowed for unequal group variances (p = 0.1), so it must be interpreted with caution.
The difference between parent and teacher ratings deserves some comment. Parents in general reported worse ADHD symptoms in the comorbid group than in any other group and worse BPSD symptoms in the comorbid group than in ADHD alone. Teachers reported ADHD symptoms worse in the comorbid group than in the BPSD-alone group but not greater than for ADHD alone. They reported the same pattern for BPSD symptoms: worse in comorbid group than BPSD-alone group but not worse than for ADHD alone. The parental findings seem intuitive in that (i) manic symptoms were linked to BPSD either alone or with ADHD, and (ii) severity of ADHD symptoms, which might also reflect BPSD symptoms, was exacerbated by comorbidity with BPSD. Unfortunately, we have no way of knowing whether parents (and teachers) reported the mood symptoms when the child was manic, hypomanic, depressed, or euthymic. Teachers rated ADHD symptoms more severe in comorbidity than in BPSD alone; this is compatible with the parent report and common sense. However, teachers did not rate ADHD symptoms more severe in the comorbid group than in the ADHD-alone group as parents did. Even more notable, teachers reported manic symptoms as more severe in the comorbid children than in BPSD-alone but not more severe than in the ADHD-alone group.
This difference between parent and teacher ratings is an unexpected finding. To make sure the difference between parent and teacher ratings of manic symptoms was not a function of biased missing data (the n for teacher data was 466 compared to 692 for parent data), we repeated the parent-rated manic symptom analysis using parent ratings only from the subgroup that also had teacher ratings. The results showed essentially the same pattern as the whole sample. If this difference is replicated, it may reflect the following explanations, in order of probability: (i) Teachers tend to be better educated about, and more sensitized to, ADHD symptoms than bipolar symptoms, and might conflate ADHD symptoms with bipolar symptoms (42
). In fact, Youngstrom et al. (42
) and Kahana et al. (43
) reported that teacher ratings for children with ADHD and BPSD look similar. Learning about ADHD is now a standard part of teacher training and it would be rare for BPSD to receive the same attention, so this possibility seems strong. (ii) There are undoubtedly different priorities for behavior in school than at home; this also seems an established fact. (iii) There are often actual differences in home and school behavior (24
). (iv) Somewhat less likely, informant perception may be colored by prior experience (i.e., the parent having a longer history with the child, including better opportunity to note mood episodes). (v) Although the type of school setting could make a difference, with special education teachers having a higher behavioral threshold for significant ratings, this is unlikely to explain the parent-teacher difference.
Generally, for ADHD symptoms teacher observations are considered more valid and sensitive to treatment effects because they have more experience with norms
(other children), actually have age peers available for real-time comparison, see the child in task-demand situations that tend to bring out ADHD symptoms, and are usually more emotionally neutral and objective. These advantages may not apply to observation of mood states, in which parents, who see the child more hours per week and have a longer historical exposure to the child’s usual state, may have an observational advantage (42
). This issue warrants further study.
The fine-grained examination of individual ADHD and manic symptoms in revealed some interesting comparisons that appear to depend on how a question is framed; these have clinical diagnostic implications. When distractibility is asked about as a trait (Is easily distracted
), ADHD either alone (86%) or with BPSD (94%) showed almost twice the prevalence found in BPSD alone (51%). But when asked about as a state (Is far more distractible than usual
), the prevalence drops to 33.5% in ADHD alone, less than in BPSD alone (40%) and about half the rate in the comorbid group (62%). It is curious that even though the trait of distractibility is already high in ADHD, an increase in distractibility is noted substantially more often with the two disorders combined than with BPSD alone. A similar phenomenon can be noted for talks excessively
vs. much more talkative than usual
and for fidgets/squirms, difficulty remaining seated, runs/climbs
, and on the go/driven by a motor
versus more active/busy than normal
. These contrasts suggest that the extensive symptom overlap between ADHD and BPSD need not constitute a serious impediment to diagnostic distinction if questions are framed carefully (41
). The pattern is consistent with the idea that ADHD has a more chronic presentation, whereas mood disorders tend to have a more episodic, fluctuating presentation (7
). Of course ADHD symptoms alone, no matter how severe, cannot alone justify a BPSD diagnosis without specific mood symptoms and episodicity. Nevertheless, it seems clear that all ADHD symptoms trend worse in the comorbid condition and some but not all manic symptoms also do. This, of course, is not specific to BPSD: ADHD symptoms get worse with depression, anxiety, or substance abuse, and during family conflicts or environmental stressors.
This difference in question formulation is critical clinically for distinguishing BPSD from ADHD. As explained in the method section, it is important to determine whether a symptom is worse during a mood episode, or possibly even restricted to the mood episode, before counting it towards a mood diagnosis. As defined in DSM-IV, ADHD is a chronic pattern of behavior, whereas BPSD is characterized by episodes of mood change (mood elevation or depression, uncharacteristic silliness, racing thoughts, etc.) with increases in troublesome activity, inattention, and other symptoms that in more chronic form characterize ADHD.
The data presented here were collected once, at the baseline assessment, so any conclusions about longitudinal course, progression, or causality must be considered speculative. The same sample is being followed longitudinally with periodic assessments that will allow a careful examination of progression and course. The sample was enriched for symptoms of mania and, thus is not representative of the whole child mental health clinic population. Rather, it is mainly representative of the subgroup of the child mental health clinic population that presents at first appointment with elevated symptoms of mania. For this reason, the proportions with BPSD and with ADHD (for which most, perhaps all, symptoms are similar to bipolar symptoms) are probably higher than in the general child mental health clinical population. Nevertheless, the actual diagnoses were carefully made by experienced research diagnosticians using information from reliability-trained interviewers, so that the comparisons between diagnoses should be valid. The small number (45
) with BPSD without ADHD impaired power for some comparisons, possibly allowing some type 2 errors. The number of comparisons made also invited type 1 error, but we partially corrected for this by using Holm’s stepdown Bonferroni correction for the exploratory comparisons (those not testing an a priori hypothesis), with corrected nonsignificance indicated by a superscript ‘b’ in and a superscript ‘c’ in . Finally, this sample started at age 6–12, missing the early stages of ADHD and not yet tapping adolescence. Therefore, in addition to the prospective assessments being carried out on this sample, it would be desirable to recruit a sample aged 3–6 at baseline with ADHD and follow them prospectively.
In sum, these analyses of 707 carefully diagnosed children failed to find an excess of overlap between ADHD and BPSD or the expected earlier age of BPSD onset with comorbid ADHD, but did find greater symptom severity, greater functional impairment, and more additional comorbidity in the comorbid ADHD + BPSD group.