What are the signs and symptoms of Sensory processing disorder?

Sensory integration difficulties or sensory processing disorder (SPD) are characterized by persistent challenges with neurological processing of sensory stimuli that interfere with a person's ability to participate in everyday life. Such challenges can appear in one or several sensory systems of the somatosensory system, vestibular system, proprioceptive system, interoceptive system, auditory system, visual system, olfactory system, and gustatory system.
While many people can present one or two symptoms, sensory processing disorder has to have a clear functional impact on the person's life:
Signs of over-responsivity, including, for example, dislike of textures such as those found in fabrics, foods, grooming products or other materials found in daily living, to which most people would not react, and serious discomfort, sickness or threat induced by normal sounds, lights, ambient temperature, movements, smells, tastes, or even inner sensations such as heartbeat.Signs of under-responsivity, including sluggishness and lack of responsiveness.
Sensory cravings, including, for example, fidgeting, impulsiveness, and/or seeking or making loud, disturbing noises; and sensorimotor-based problems, including slow and uncoordinated movements or poor handwriting.
Sensory discrimination problems, which might manifest themselves in behaviors such as things constantly dropped.
Symptoms may vary according to the disorder's type and subtype present.
Sensory integration and processing difficulties can be a feature of a number of disorders, including anxiety problems, attention deficit hyperactivity disorder (ADHD),food intolerances, behavioural disorders, and particularly, autism spectrum disorders. 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.

While many people with Sensory processing disorder can present one or two symptoms, it has to have a clear functional impact on the person's life:
Signs of over-responsivity, including, for example, dislike of textures such as those found in fabrics, foods, grooming products or other materials found in daily living, to which most people would not react, and serious discomfort, sickness or threat induced by normal sounds, lights, ambient temperature, movements, smells, tastes, or even inner sensations such as heartbeat.Signs of under-responsivity, including sluggishness and lack of responsiveness.
Sensory cravings, including, for example, fidgeting, impulsiveness, and/or seeking or making loud, disturbing noises; and sensorimotor-based problems, including slow and uncoordinated movements or poor handwriting.