A mattress's firmness can significantly impact the ability to get comfortable if you have a herniated disc. A soft mattress may cause your body to sink in the wrong places and put added pressure on the painful area. A medium to firm mattress can help keep your spine in a neutral alignment and help you rest more comfortably.A mattress's firmness can significantly impact the ability to get comfortable if you have a herniated disc. A soft mattress may cause your body to sink in the wrong places and put added pressure on the painful area. A medium to firm mattress can help keep your spine in a neutral alignment and help you rest more comfortably.