In children and adults with ADHD, preliminary research has found hypo- and hyper-responsiveness to sensory stimuli, as well as difficulties moderating sensory input. This is most likely due to the inability to filter out irrelevant sensory stimuli from important stimuli.

Both Sensory Processing Disorder (SPD) and ADHD can cause a person to feel restless and unable to concentrate or relax. SPD is a common co-occurrence with ADHD, but can occur on it's own. This can sometimes lead to a misdiagnosis of ADHD especially in children as the child could be simply unable to sit still or focus due to their overstimulation.

Some symptoms of Sensory Processing Disorder are:

• Picky eating habits, particularly avoiding foods with textures that the person finds unpleasant

• Trouble settling down after activities

• Sensitivity to smells or sounds

• Dislike of certain fabrics, clothing items, or shoes

• Discomfort with certain movements, like swinging or riding an elevator

People with ADHD and SPD are much more prone to Sensory Overload. These are some of the ways each of the senses can overload someone with ADHD.

Touch 

The texture of certain foods, fabrics or body washes can overwhelm people with ADHD. This is one of the most common sensory overloads for kids with ADHD, and girls may be particularly at risk. The way that certain clothes or shoes fit can be frustrating and overwhelming, particularly for kids. Others might experience overwhelm from bed sheets or car seats.

Taste 

Some people with ADHD are sensitive to certain tastes, although food aversions are more commonly caused by textures.

Sound 

Loud noises like a fire alarm or even subtle noises like someone chewing can cause stress. Some people with ADHD have issues in loud restaurants or parties because of all the sounds.

Smell 

People with a sensory processing disorder might be especially sensitive to smells, even those that are meant to be pleasant, like perfume or cooking food.

Sight 

Visual clutter can provide too much stimulation. This can be especially caused by the ADHD's lack of organization skills. Visual overstimulation can also be an issue at large gatherings or places like theme parks or casinos.

Personal Experience

I will get sensory overload anytime I'm in a large group of people. Oftentimes I have trouble focusing on the people who are trying to talk to me and my focus will shift to the many conversations happening around me. I also get overloaded trying to look at all the people and watch what they are doing while also trying to have situational awareness. I often have to have someone tell me that there is someone behind me trying to get by or prevent me from turning and running into someone else when I'm in public.