Minister for Disabled People, Esther McVey, has told Daybreak that the changes will focus benefits on those who need them most.
She said: "Disability Living Allowance (DLA) came out in the 1990s and it was very much about physical disabilities.
"Now we're adjusting it to take into account disability how we understand it today - mental disabilities as well as fluctuating ones.
"So it is actually understanding disabilities more and it is really focusing benefits to where it's needed most."
More top news
Vacuum cleaner manufacturer Dyson has said that it will invest £2 billion in electric car development.
Victims have won a ruling allowing them to launch a High Court group action seeking damages over contaminated blood products.
Jaffa Cake fans have been left outraged after boxes of the biscuits dropped in size from 12 to 10.