After Peter exposed Norman to one of his own pyschadelic weapons in the Spectacular Spider-Man Magazine #2, Norman's memories of the Green Goblin were gone. This bought Peter some time, but it did not negate the possibility of Norman returning to the role of the Green Goblin once again. In the infamous "Not Approved by the Comics Code Authority" story arc featured in Amazing Spider-Man #96-98, Harry Osborn falls victim to drugs (in the form of unnamed pills) a struggle that will persist for rest of his life.
Amazing Spider-Man #96 begins with Harry Osborn recommending that Peter accept the job offer that his father gave him at one of his chemical companies. Peter is hesitant at first, but then decides that he will go ask Norman for a part-time position. When Peter arrives to see Norman he notices that Norman is being treated by his doctor. The doctor recommends that Norman not think about crime or super heroes, because those thoughts negatively affect his blood pressure. Norman then proceeds to offer Peter a position and the two discuss attending Mary Jane's show that is later that evening; Norman is going to meet her for the first time. While everyone is gathering before the show, Norman and Randy Robertson get into a heated discussion as Randy claims that anyone with money and power is responsible to help with social reform. Osborn claims that he had worked hard for what he has and that he has no "forced obligation" to society, the conversation escalates and eventually Harry is forced to separate the two.
Norman's delicate disposition is beginning to waver and as they approach the theatre he is strangely affected by a door that he doesn't completely recognize. After the show Norman takes off without saying goodbye and later returns to the mysterious door. Peter, suspicious of Norman's odd behavior, follows him. When Peter arrives the Green Goblin bursts through the door, which was a secret passage to one of his Goblin hideouts.
Amazing Spider-Man #97 picks up immediately following the events of the previous issue as Spider-Man attacks the Green Goblin, who is "madder" than ever. The Goblin exposes Spidey to more hallucinogenic gas, making him vulnerable to an attack. After watching Spidey fall, he was convinced that the web-slinger had plummeted to his death, so the Goblin took off to "follow [his] destiny". However, the Goblin should have performed a more thorough search, usually Norman is quite thorough, because the wall crawler did not die during his fall. Instead, he clung to the wall of a building as he watched the Goblin head off on his glider.
Whilst the Green Goblin believed Spider-Man to have perished, he began to wreak havoc throughout New York City. During Peter's tracking of Osborn he noted that the newspapers announced a 'mysterious wave of assaults and hijackings' all over town. This was the apparent handiwork of the Green Goblin, who was clearly in a reckless state of mind and almost looking to get caught by authorities. Meanwhile, Harry Osborn, distraught by the news from MJ that she not "anybody's girl", turns to drugs to overcome the emotional setback. This sends Harry into a whirlwind of drug hallucinations that leave him weak and in need of medical attention, luckily Peter was there to help Harry. Unfortunately for Peter, the Goblin arrived at the apartment as well to finish off his arch nemesis!
In the third installment of this story arc, Amazing Spider-Man #98, Peter is there to help Harry, but the Green Goblin soon arrives prepared to finish off Peter once and for all. Peter shows the Goblin his son in an attempt to make Norman "snap out" of his Goblin persona. In an interesting turn of events the Goblin states that he does not recognize that person that Peter is holding. This begs the question, what all did he forget in regards to Norman Osborn once he remembered he was the Green Goblin? When he was aware of the Goblin in the past, he knew that he was Norman Osborn. One thing is for certain, Norman's mental state was totally out of whack at this point as he did not recognize Harry as his son, which is something he should have certainly been aware of as the Green Goblin or not.
The Goblin, unwilling to face the truth takes off before Peter can stop him. After kicking the ass (sorry butt) of the drug dealer that sold Harry the pills, Peter decides he has to face Norman again. But before Peter can find Norman, Norman finds him! The Green Goblin ambushed Spider-Man high above the streets of New York City and the web-slinger was certainly caught off-guard. The two battled once again and the Goblin exposes Spidey to a mist that stops him from being able to stick to walls. Spider-Man overcomes this obstacle using his Spider strength and agility to gain control of the Goblin Glider and forces Norman to face his son. He takes Norman to the hospital window that looks into Harry's room, this causes another emotional breakdown in Norman, he falls unconscious once again and forgets being the Green Goblin for a third and final time.
Also, it is rather likely that around this time Gwen Stacy gave birth to Norman's twins, Sarah and Gabriel. Norman and Gwen had conceived these children when they had a secret affair around the time of Amazing Spider-Man #61-63. Gwen gives birth to the twins in secretly in France and the children remained there when she returned to the U.S., the exact timeline for these events is unclear. The children were born two months early, yet they were fully grown at birth. Norman's altered genetic makeup, due to the Goblin formula, was the cause for the rapid aging. Gwen, fearing a fate for her children similar to Harry Osborn, insisted that Norman not be involved with raising them. This all changes with the events of Amazing Spider-Man #121.
Later, Norman appears to have recovered and returned to a normal life. In fact, he makes two brief appearances in the Spiderverse after this event which indicate that he's fully functional again. The first, in Amazing Spider-Man #105, depicts Norman taking Harry to a surprise party in which all of Harry's friends are in attendance. The second is in Amazing Spider-Man #117 in which Norman is discussing the New York City mayoral candidate with J. Jonah Jameson and Joe Robertson. Although this was Harry's first bout with drugs, his second one will tip Norman over the edge for good, sending shockwaves through the Spider-Verse.
Norman offers Peter a job and tosses a few compliments his way, as seen in Amazing Spider-Man #96
Amazing Spider-Man #96
Amazing Spider-Man #97
Amazing Spider-Man #97
Amazing Spider-Man #97
Amazing Spider-Man #98
Amazing Spider-Man #98
above: Spider-Man forces the Green Goblin to confront his son
below: Osborn begins to break down and once again forgets that he is also the villainous Green Goblin, both panels are seen in Amazing Spider-Man #98
A mentally fit Norman Osborn is discussing politics with his peers, as seen in Amazing Spider-Man #117