What are the implications of only doing 6GCSEs

Not at all
My DD isn't going to pick a language gcse, it doesn't interest her

I don't think so as long as they get maths and English and good enough grades in the subjects they want to do for A level.
University won't care about GCSEs once they have A levels

That's fine. The basic minimum for most next-step options is to have 5 GCSEs at grade 5 or better (some options are OK with grade 4 or better) which must include English&Marhs so doing 6 is perfectly ok.

If doing A-Levels he should have at least grade 6 but ideally grade 7 or more in the related GCSE (if getting grade 6 was the best they could do at GCSE with a lot of hard work then they will be likely to get around grade C at A-level - respectable enough but will be aiming for lower-tier universities). Grade 8 or 9 at GCSE will mean a reasonable chance at top A-Level grades. Grade 5 or lower will mean they are unlikely to cope with the A-Level course at all.

Double Science is fine for progressing to A-Level. The difference between double and triple science at GCSE is that they cover the topics to the same depth but with narrower breadth (ie fewer specific topics within each science). It won't matter at A-Level because the teaching will start from scratch on each topic (although at a fast pace) because each exam boad will have done different topics at GCSE so the A-Level teacher won't assume significant prior knowledge but will assume enough familiarity with the subject in general that any student who didn't cover the topic at GCSE level can catch up quickly.

Gosh, I'm so sorry to hear that. No, definitely don't worry about that at all, was just a suggestion in case they were already doing things they could include. Good luck, we will all be here thinking of you. Any qualifications they manage to get at such a difficult time is amazing, and a testament to their resilience. I've always reassured students in the past (when they have been struggling) is to give the exams their best effort but don't see it as a final line as they can retake.

Indeed - I did two "extra" GCSEs than most of my peers (11 rather than 9, 9 was standard in my school) and looking back I think...wtf was the point?! No-one's ever cared about my extra GCSE is Spanish...

No bad implications, they can still successfully go onto a levels, and university, if that what they want to do. As long as they have English and maths, and science in your son’s case, the rest doesn’t really matter. Having 10-12 GCSEs is lovely, but it’s absolutely no guarantee of success in life, later on.

Health first. Education can come later.

Getting into a school where he is happy (ish) and coping is much better than worrying about the number of subjects. And if he isn’t coping then health always comes first. If he has the interest then online school might be an option.

(My teen daughter was suicidal aged 15 and had to pull out of school to be closely watched - she is now 23 and thriving and doing her PhD.)

Look after yourself as well.

Absolutely fine. No foreign language needed. Heads-up though, physics a level will need at least a 7 in both maths and sciences and is almost exclusively studied alongside a level maths. Not taught a student yet who thrived at physics a level unless they did a level maths too. Sounds like they will be totally fine. Lots of home educated students accepted into schools for 6th form too now. No longer unusual.

It's absolutely not essential if it's not the right thing for their health.

Extracurricular doesn't matter a jot for entrance to universities apart from a few subjects like medicine where they need work experience or similar - it's subject interest they care about. So reading some books about physics or whatever degree they end up applying for and making some reference to a particular section of the book that interested them would be just fine for their personal statement.

Double science is also fine - some mainstream schools don't bother offering the triple.

But it's also fine if what your DC needs now is a bit of time out and restart thinking about qualifications when they're well. Just saying that because I wish someone had told 16yo autistic me that. Sorry for the situation you're in OP

I’m really sorry to hear your child is in such a difficult place. I hope things improve soon.

I do have a question about the choices they’ve made as certainly on the curriculum our school follows there is a lot of extra curricular PE needed as part of fulfilling the passing requirements - I think it’s either participating in two or three sports regularly. Will they be able to complete this? Would another subject be a better option if they’re struggling with the extra curricular part?

Maths, English and at least double science. It's essential you get them back into school as soon as possible.

My child did six for very similar reasons and is now applying to good universities for a stem subject . It won't make any difference, better 6 good grades than 9 not good.

It is very very tough I know.

I think given your update, your DC needs to do what they can cope with and no more. Help them survive and thrive emotionally, and to not put undue pressure on themselves.
It's not like it used to be. There are many paths to a good education and it doesn't all have to be on the traditional time scale.

Oh sorry, just realised you listed 6 aside from DofE. That would be fine for A levels

Most places (there are some exceptions) do not count DofE as a GCSE equivalent so that would be my main worry here. There’s no issue doing A level sciences after dual award unless in the chosen setting there are other students who have done separate sciences: in that case the pupils who have done dual often have to attend separate classes to cover the material that the others have already covered; this can usually be done in a term though.

I've been there , it's really tough.

My son didn't have extra curricular because he couldn't do anything else either. His personal statement focused entirely on his academic subject.

Double science is fine is you can get grade 7 or more. Some will accept lower for A level but the course content may be challenging and a good grade tricky. Six gcses will be sufficient in most cases as long as it includes core subjects and are good grades for any subjects relevant to the A level subjects. Schools tend to want 8 for their stats. D of E is unnecessary apart from for personal development but can attract ucas points if that is relevant later on to meet entry requirements. However the majority if unis specify grades not points and won't be interested.

No. The usual requirements are 5 GCSEs. For A levels you'd usually be expected to have grades 6-9 in those. Just doesn't leave much room for a crap grade if that makes sense?

My son didn't do a language.

Check entry requirements for specific courses but my DS only did 6 for very similar reasons and was interviewed by Oxford for his chosen subject and now is at UCL in his first year. It hasn't held him back whatsoever.

If he wants to do a science degree you might want to just check whether he needs to do 3 sciences as part of the 6.

Loads of kids don't do a language GCSE.

6 is fine, you should make sure English Language, Maths and Science are taken though as most colleges and employers expect that. Context is always important so keep a bit of a CV going too - any clubs or experience etc. Good luck