Attorney Paul Stracci said those conditions led to Schaap's "aberrant" behavior with the girl who turned 17 during the four-week relationship.
"Unfortunately, for a four-week period during the summer of 2012, he acted in a manner contrary to the entire balance of his life by engaging in sexual activity with a young woman with whom he had only recently come to counsel," Stracci wrote in the memorandum.
Schaap, 55, of Dyer, also was being treated for chronic and acute inflammation of his prostate, according to the memo.
Schaap was fired by the church in July and pleaded guilty in September to taking a minor across state lines — to adjacent suburban Chicago and to northern Lower Michigan — with intent to engage in criminal sexual activity.
Stracci filed 140 letters of support with the sentencing memorandum. They include ones from Schaap's wife, Cindy, and other family members; staff of the church and its college, Hyles-Anderson College; pastors from across the country and missionaries in Ghana; and parishioners and community members.
In part because of the size of the filing and time needed to respond to it, Assistant U.S. Attorney Jill Rochelle Koster asked Judge Rudy Lozano for a 45-day continuance in Schaap's sentencing. It's currently scheduled for Jan. 15.
Also, an attorney representing the girl and her family needs additional time to prepare a victim impact statement and to calculate restitution for counseling and other services, Koster said.
But Koster wrote in her motion that the defense has told her it will object to a sentencing delay because Schaap "is anxious to be sentenced and transferred from the Porter County Jail to a Bureau of Prisons facility."
Schaap, a native of Holland, Mich., became pastor of First Baptist Church of Hammond in February 2001, a month after his predecessor and father-in-law, the Rev. Jack Hyles, died of a heart attack. Hyles' charismatic leadership as pastor beginning in 1959 helped it grow into a megachurch with hundreds of church buses transporting thousands of worshippers across northwestern Indiana and Chicago's south suburbs to what it billed as the "World's Largest Sunday School."
Besides the college, the church also operates two K-through-12 schools in the Hammond area and has hosted large conventions of religious leaders.
First Baptist's website states that under Schaap, the church moved into a new 7,500-seat auditorium, doubled its average weekly attendance and sent mission teams to Africa, Thailand and India.