You really do have to split out this whole issue of telling "lies" into multiple separate items. Because it makes a HUGE difference in how it gets handled and why, depending on the flavor.
For example
a) Lie to cover your own butt: in order to do this, you HAVE to know what you did/didn't do. This type always has a direct benefit to the person telling the lie (if it works). THESE ones, we take seriously, and treat as LIES.
b) Lie to fill in the gaps because you don't remember: insisting on the truth just makes it messier, they really DON'T remember... so, is it really a lie? (we make a distinction between a "lie", which is deliberate, and a "mis-truth", which is inaccurate but not deliberate)
c) Lie to try to make yourself look better, even when it doesn't work: really, that's a social skills issue, or a developmental issue, or a theory of mind issue, or such like. They need to learn that it always comes back to bite them, etc. But there often is no direct benefit and possibly subtle negatives... treating these like class-1 LIES doesn't help, AND doesn't teach the related skills.
Therapies and/or medications CAN sometimes help with memory-gap lies, by addressing the memory issues, or by reducing stress (which affects memory).
For example
a) Lie to cover your own butt: in order to do this, you HAVE to know what you did/didn't do. This type always has a direct benefit to the person telling the lie (if it works). THESE ones, we take seriously, and treat as LIES.
b) Lie to fill in the gaps because you don't remember: insisting on the truth just makes it messier, they really DON'T remember... so, is it really a lie? (we make a distinction between a "lie", which is deliberate, and a "mis-truth", which is inaccurate but not deliberate)
c) Lie to try to make yourself look better, even when it doesn't work: really, that's a social skills issue, or a developmental issue, or a theory of mind issue, or such like. They need to learn that it always comes back to bite them, etc. But there often is no direct benefit and possibly subtle negatives... treating these like class-1 LIES doesn't help, AND doesn't teach the related skills.
Therapies and/or medications CAN sometimes help with memory-gap lies, by addressing the memory issues, or by reducing stress (which affects memory).