The multiple sclerosis (MS) charity, MS Ireland, is reminding people that many of the symptoms of the condition can be invisible, making it difficult for those affected to explain its true impact.

May 30 is World MS Day and the theme of this year's event is visibility and giving a voice to those affected.

"While many people are aware of MS and the more visible, tangible symptoms that it can cause, the effects can vary greatly from person to person and can often be invisible to those around them. Through our World MS Day activity, we hope to raise awareness around the less visible aspects of MS and how it can impact on the day-to-day life of a person living with the condition," explained MS Ireland CEO, Ava Battles.

MS is a chronic disease of the central nervous system, which causes a gradual degeneration of the nerves. This results in a progressive deterioration in various functions controlled by the nervous system, such as vision, speech and movement.

It is usually diagnosed between the ages of 20 and 40 and is the most common debilitating neurological condition affecting young adults in Ireland. Around 9,000 people are affected here.

Recent research carried out by MS Ireland and Novartis found that while most people said they were aware of the neurological condition, almost one-third could not name a single symptom.

MS Ireland emphasised that while some symptoms of the condition are immediately obvious, such as reduced mobility, there are many invisible symptoms that can be difficult to explain to others, such as memory problems, concentration problems and fatigue.

In fact, the research found that just 8% of people knew that fatigue was a key symptom, despite the fact that 90% of people living with MS experience it.

According to world MS ambassador, Sharon Henvey from Meath, who has lived with the condition for 10 years, World MS Day is very important to her and her family.

"It's a day that shines a spotlight on the 9,000 people in Ireland living with MS and what life is like for us. The theme for this year's campaign is visibility, which I think is crucially important, as some of the symptoms I experience are unseen.

"I do at times feel that my MS is invisible, which can be hard to explain to friends and family, so hopefully this campaign can create awareness of these unseen symptoms," she said.

For more information on World MS Day, click here. For more information on MS Ireland, click here.