This pattern of comorbidities poses a significant challenge to those who claim that SPD is an identifiably specific disorder, rather than simply a term given to a set of symptoms common to other disorders.Two studies have provided preliminary evidence suggesting that there may be measurable neurological differences between children diagnosed with SPD and control children classified as neurotypical or children diagnosed with autism. Despite this evidence, that SPD researchers have yet to agree on a proven, standardized diagnostic tool undermines researchers ability to define the boundaries of the disorder and makes correlational studies, like those on structural brain abnormalities, less convincing. Causes
The exact cause of SPD is not known. However, it is known that the midbrain and brainstem regions of the central nervous system are early centers in the processing pathway for multisensory integration; these brain regions are involved in processes including coordination, attention, arousal, and autonomic function. After sensory information passes through these centers, it is then routed to brain regions responsible for emotions, memory, and higher level cognitive functions. Damage in any part of the brain involved in multisensory processing can cause difficulties in adequately processing stimuli in a functional way. Mechanism
Research in sensory processing in 2007, is focused on finding the genetic and neurological causes of SPD. Electroencephalography (EEG), measuring event-related potential (ERP) and magnetoencephalography (MEG) are traditionally used to explore the causes behind the behaviors observed in SPD. Differences in tactile and auditory over-responsivity show moderate genetic influences, with tactile over-responsivity demonstrating greater heritability.
The following link is a fact sheet regarding the role of Occupational Therapy in treating sensory processing disorder: https://www.aota.org/-/media/corporate/files/aboutot/professionals/whatisot/cy/fact-sheets/factsheet_sensoryintegration.pdf
   Although Ayres initially developed her assessment tools and intervention methods to support children with sensory integration and processing challenges, the theory is relevant beyond childhood.Sensory integration therapy is driven by four main principles:
Just right challenge (the child must be able to successfully meet the challenges that are presented through playful activities)
Adaptive response (the child adapts their behavior with new and useful strategies in response to the challenges presented)
Active engagement (the child will want to participate because the activities are fun)
Child directed (the childs preferences are used to initiate therapeutic experiences within the session)Serious questions have been raised as to the effectiveness of this therapy particularly in medical journals where the requirements for a treatment to be effective is much higher and developed than its occupational therapy counter parts which often advocate the effectiveness of the treatment.