Q: Does bilingualism cause learning difficulties and language disorders?
A: Bilingualism in a family neither increases nor reduces the chance of experiencing language difficulties and language disorders. The bilingual child may, for example, be diagnosed as dyslexic, aphasic, have partially hearing or a low IQ score, just like any other child. If your child is diagnosed with a problem, you need to make sure that the specialist who is diagnosing your child has studied bilingualism in their professional training, and has experience of dealing with bilingual children. They should be able to reassure you that bilingualism is typically not the cause of the problem - and that's backed by research.
When a child is learning a second language, some temporary lags and inaccuracies are to be expected. Language disorders, on the other hand, include specific problems such as great difficulty in producing certain sounds, a considerable lack of understanding (or use) of familiar words, difficulty in remembering new words despite a great deal of exposure to them and problems with expressing needs and wants without use of gestures.
For more info see the 'Education in Welsh' section.