As others have said it really depends on the individual case. Some people its so obvious that they cannot work (like my mom). My mom applied and within three months got her SSDI because her heart is so bad she cannot do much at all.

It also depends on if you have enough doctor support behind you. You need to have alot of documentation for them. Also alot of people do not get back to them/ follow up with what they need to complete the case. And that can delay it alot.

I got mine a year to year and half after I first applied. I was denied the first time and then got an attorney and got SSDI. I was denied, IMHO, because I didnt have a long doctor history because I didnt have health coverage and could not afford to go the doctor. But was able to fix that with Medi-cal in the middle of the process and then had enough info for them. So it really just depends on the person and the case.