At the end of The Notebook, we see Allie and Noah dead together holding each other's hands. I think that Noah had been trying for a couple of times to let Allie remember everything permanently. But the expected "miracle" did not happen a single time, and every time she lost everything. Now my question is how did they die together? As this was not the first time Allie forgot everything, I don't believe it was a serious physical problem that can cause death. Apparently, Noah was also not sick, although he got a heart attack. But I believe it was out of his sorrow for again losing her. He was there to help Allie. So how come they died together? Did they commit suicide?
There is no mention of them committing suicide. The whole premise of the end of the film is that Allie remembered everything and that she and Noah died together at the same time because their love was so strong.
Allie asks Noah if he thinks their love is so strong that it can grant miracles and he says yes, which is proven by her memory returning against all odds. She then asks if their love is so strong that it could take them away together, which would be another miracle. Their dying in the next scene shows that their love was so strong that it granted the miracle of them dying together. They didn't commit suicide and there was no medical problem, it was just a miracle. It's a really cheesy plotline, but that's what was intended.
I do think that suicide is implied at the end. There is Allie's question to Noah if they can die together and his answer is that he believes they can do whatever they want to do...so just like Romeo and Juliet...
Actually only allie dies if you read the sequel. Noah lives on into the second book. He helps his son in law recapture the spark in his marriage while they plan their own daughter's wedding