اختلال نقص توجه و بیش فعالی و اختلال مدولاسیون حسی: مقایسه رفتار و فیزیولوژی

Children with attention deficit hyperactivity disorder (ADHD) are impulsive, inattentive and hyperactive, while children with sensory modulation disorder (SMD), one subtype of Sensory Processing Disorder, have difficulty responding adaptively to daily sensory experiences. ADHD and SMD are often difficult to distinguish. To differentiate these disorders in children, clinical ADHD, SMD, and dual diagnoses were assessed. All groups had significantly more sensory, attention, activity, impulsivity, and emotional difficulties than typical children, but with distinct profiles. Inattention was greater in ADHD compared to SMD. Dual diagnoses had more sensory-related behaviors than ADHD and more attentional difficulties than SMD. SMD had more sensory issues, somatic complaints, anxiety/depression, and difficulty adapting than ADHD. SMD had greater physiological/electrodermal reactivity to sensory stimuli than ADHD and typical controls. Parent-report measures identifying sensory, attentional, hyperactive, and impulsive difficulties varied in agreement with clinician's diagnoses. Evidence suggests ADHD and SMD are distinct diagnoses.

Attention deficit hyperactivity disorder (ADHD) is an early childhood developmental disorder that has received enormous attention in research. Typical characteristics of ADHD are developmentally inappropriate impulsivity, inattention, and hyperactivity (Barkley and Murphy, 1998 and Kaplan et al., 1994). ADHD is a costly and prevalent childhood disorder that affects 3–12% of school-aged children (Froehlich et al., 2007 and Schachar, 2000) and accounts for approximately half of all pediatric referrals to mental health services (CDC, 2003, Glicken, 1997 and Goldman et al., 1998). Another early childhood developmental disorder, which has received less attention, is Sensory Processing Disorder (SPD) (Miller, Anzalone, Lane, Cermak, & Osten, 2007). The essential features of SPD are the presence of difficulties in detecting, modulating, interpreting and/or organizing sensory stimuli, which are so severe that it interferes with daily life routines. The presence of sensory symptoms may be as prevalent as ADHD (Ahn et al., 2004, Ben-Sasson et al., 2009a and Gouze et al., 2009). For decades, large numbers of children have been identified as having sensory-based disorders by occupational therapy clinicians and others. Although, wide-spread skepticism exists among many health professionals about SPD and its treatment (e.g., Arendt et al., 1988, Hoehn and Baumeister, 1994, Polatajko et al., 1992, Schaffer, 1984 and Vargas and Camilli, 1999), SPD is recognized by both the Diagnostic Manual for Infancy and Early Childhood (Interdisciplinary Council on Developmental and Learning Disorders (ICDL-DMIC), 2005) and the Zero to Three Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood: Revised edition (DC:0-3R; Zero to Three, 2005), both of which focus on subtypes of one classic pattern of SPD called sensory modulation disorder (SMD). The prevalence of sensory symptoms is estimated to be 5–16% in the normal population (Ben-Sasson et al., 2009b and Gouze et al., 2009) and 30–80% in individuals with developmental disabilities (Ahn et al., 2004, Baranek et al., 1997, Ben-Sasson et al., 2009b and Tomchek and Dunn, 2007). While evidence suggests that neither ADHD nor SPD are homogeneous conditions, some of the behaviors characteristic of ADHD overlap with those observed in SPD. Therefore, one important question is whether ADHD and SPD are distinct disorders, the same disorder or manifest as co-morbid disorders. The current Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-R, 2000) does not recognize SPD as a separate clinical disorder. However, efforts have been directed toward the inclusion of SPD as a ‘novel diagnosis’ (D. Pine, personal communication). Additionally, there are questions about the validity of the traditional ADHD subtypes (e.g., Widiger & Samuel, 2005). Three ADHD subtypes are described in the current DSM-IV-R: predominantly inattentive; predominantly hyperactive and impulsive; and combined inattentive and hyperactive/impulsive. ADHD/hyperactive impulsive (ADHD/HI) is characterized by excessive and situationally inappropriate motor activity (Halperin, Matier, Bedi, Sharma, & Newcorn, 1992) and limited inhibitory control of responses (Barkley, 1997, Chelune et al., 1986 and Nigg, 2000), whereas ADHD/inattentive (ADHD/I) is characterized by an impaired ability to focus, sustain, and switch attention (Cepeda et al., 2000, Levine et al., 1982 and Seidel and Joschko, 1990). Some children have both types of ADHD referred to as ADHD/combined (ADHD/C). Children with all types of ADHD face daily challenges with learning and achieving at school, behaving appropriately at home, and participating fully in their communities due to difficulty controlling impulsive behavior, sustaining attention, and regulating activity levels. One primary pattern within SPD is sensory modulation disorder (SMD), which is characterized by difficulty regulating and organizing responses to sensory input. SMD includes three subtypes delineated by a recent nosology (Miller, Anzalone, et al., 2007) as well as in two developmental diagnostic manuals for young children (ICDL-DMIC, 2005 and Zero to Three, 2005): Sensory-Over-Responsivity (SOR), Sensory-Under-Responsivity (SUR), and Sensory-Seeking/Craving (SS/C). Children with SOR feel sensations too intensely, for a longer duration than is typical and/or may over-respond with atypical behaviors such as temper tantrums, screaming or moving away from stimulation. Often these children try to keep their behaviors under control at school where they are exposed to multisensory input, only to become disregulated when they come home. SUR describes children who respond less to or take longer to respond to input. These children often appear withdrawn or seem to be “in their own world.” They have difficulty listening, following directions, knowing where there body is in space, and initiating movement. SS/C describes children who seek out high intensity or increased duration of sensory stimulation. They have behaviors such as constantly being on the move, falling down or crashing into people or the floor, staring at optical interests for an extended time period, or craving touch so much that they are in everyone else's space and face continually in an effort to gain more sensory information. Identification of SMD/SPD is only made when the resulting behaviors significantly affect a child's daily life (Bar-Shalita et al., 2008 and Parham and Johnson-Ecker, 2000). The overlap of symptoms in children with SMD and ADHD makes it difficult to differentiate the two disorders. For example, children with SMD who are SS/C often have attentional difficulties, poor impulse control, and hyperactivity (Mulligan, 1996 and Smith Roley, 2006). Likewise, children with ADHD may have sensory symptoms characteristic of SMD (Ahn et al., 2004). For example, problems with sensory-over-responsivity (Barkley and Murphy, 1998 and Lucker et al., 1996), especially in the somatosensory system (Castellanos et al., 1996, Parush et al., 1997, Parush et al., 2007, Reynolds and Lane, 2008, Reynolds and Lane, 2009 and Shochat et al., 2009) have frequently been reported in children with ADHD. Additionally, some behavioral descriptors for ADHD and SMD are strikingly similar. SS/C and ADHD/HI both include poor impulse control, inappropriate movement and touch; sensory over-responsivity and ADHD/I both include behaviors such as distractibility and difficulty focusing; and sensory under-responsivity and ADHD/I both include being unaware when spoken to or asked to follow directions. Although some behavioral characteristics of ADHD and SMD overlap, we hypothesize that the physiological reactions to sensory stimuli differs between children with ADHD and those with SMD. Sympathetic markers of nervous system function, assessed using electrodermal activity (EDA), have been used to characterize “flight or flight” reactions of children with SMD in response to sensory stimuli (McIntosh, Miller, Shyu, & Hagerman, 1999). EDA evaluates the skin's electrical conductance associated with changes in eccrine sweat gland activity in reaction to novel, startling or threatening stimuli, aggressive or defensive feelings (Fowles, 1986), and positive and negative emotional events (Andreassi, 1986). EDA includes measures of arousal (e.g., tonic skin conductance level), and reaction to stimuli (e.g., phasic skin conductance responses). Children with SMD are reported to exhibit large EDA responses to sensory stimuli, suggesting stronger physiological reactivity compared to typically developing children (McIntosh et al., 1999b and Miller et al., 2001). EDA has also been used to characterize children with ADHD. Early studies suggest that children with ADHD show smaller phasic reactivity to stimuli compared to typically developing children (Rosenthal and Allen, 1978, Spring et al., 1974 and Zahn et al., 1975). However, recent research suggests a disagreement remains as to whether the physiological reactivity of children with ADHD is smaller (Mangeot et al., 2001 and Shibagaki et al., 1993) or the same (Herpertz et al., 2003) as typically developing children. Likewise, studies differ on whether tonic arousal is lower in ADHD children (Beauchaine et al., 2001, Lawrence et al., 2005, Lazzaro et al., 1999 and Shibagaki and Yamanaka, 1990) or similar (Pliszka et al., 1993, Rapoport et al., 1980 and Satterfield et al., 1984) to typically developing children. It is likely that variability between studies, especially differences among the ADHD samples contributed to the inconsistent findings. Thus, the need exists to differentiate ADHD from SMD both behaviorally and physiologically. This study sought to evaluate areas that may discriminate and overlap the two conditions using subjective measures of behavior as well as objective physiological measures of sensory reactivity to a variety of sensory stimuli. A sample of children with documented clinical diagnoses of ADHD, SMD, or a dual diagnosis of both, were evaluated for the presence of sensory sensitivities and for atypical attentional behaviors using parent-report measures. The association between clinician's diagnoses and identification of ADHD, SMD, or both based on results of parent-report measures were also evaluated. Additionally, electrodermal activity measured physiological reactivity to sensory stimuli.

The current study provides preliminary results suggesting that ADHD and SMD are separate dimensions and may be different diagnostic categories. Although co-morbidity does exist in some children with SMD and ADHD, individuals with attentional, hyperactive and/or impulsive issues without sensory problems and individuals with the converse appear to be separable. Children with ADHD significantly differed from children with SMD on measures of emotional, attentional, and sensory-related behaviors as well as physiological reactivity to sensory stimuli. Differentiation of ADHD and SMD has critical treatment implications. While both clinical disorders impair social, academic or occupational functioning, children with ADHD typically benefit from medication (Benner-Davis and Heaton, 2007, Chavez et al., 2009, Findling et al., 2008 and Soileau, 2008) or therapies that focus on cognitive strategies to improve attention, hyperactivity and impulsivity (e.g., Kaiser et al., 2008, Munoz-Solomando et al., 2008 and Rader et al., 2009). Whereas, children with SMD benefit from Occupational Therapy using a sensory-based approach (Koomar and Bundy, 2002, Miller et al., 2007a and Miller et al., 2007b), which enhances a child's ability to modulate behavior in response to the ever changing sensory environment and to participate more fully in activities at home, school and in the community.