Schrader was 26 and homeless when he began work on the project and admits his own desperate and lonely circumstances fuelled the development of Robert De Niro's iconic character, Travis Bickle.
But the idea to make Bickle a New York City cab driver only came to Schrader while he was receiving urgent medical care.
He tells WENN, "It was written as a form of therapy. I was in a dark and desperate place. This character (Travis Bickle) was starting to take over my life so I felt I had to write so I would be healthy.
"I was not a screenwriter at that time, I was a film critic. I had been living in my car drifting around and I went to the hospital and I had a bleeding ulcer at the age of 26. When I was in the hospital this metaphor occurred to me of the taxi cab, this idea of this man in his metal car floating through the sewers of the city, who seems to be in the middle of society but in fact is desperately in love.
"Writing the script really helped me. After I wrote the script I drifted around the country for about six months and got myself back together and came to Los Angeles and through running into (director) Brian De Palma I gave the script to Scorsese."
The Oscar nominated drama, regularly named as one of the greatest American films ever made, has been digitally restored and is returning to select U.S. cinemas this year (11) to mark the movie's 35th anniversary.