When their children were young, Karen and David took them to a noisy restaurant. Their two-year-old daughter was being loud and excitable, as toddlers tend to be, and David suddenly got up and walked out. There were many incidents like that during their first 12 years of marriage, which would often leave David feeling frustrated, and Karen sad, lonely and confused.

Then, when their son was diagnosed with autism spectrum disorder (ASD) – the term now widely used for all autism diagnoses, including Asperger syndrome – it became clear that David had the condition, too. Eventually, he had a formal diagnosis. Their marriage is much happier. “I am now much better equipped to understand why I may find neurotypical relationships so confusing,” says David, “and it has been the foundation of improving my relationship with Karen.”

Karen says she often used to feel exasperated by David’s mood swings and what she saw as his tendency to blow small problems out of proportion. “I couldn’t understand it because he was the most loving, generous person much of the time.”

Thanks to the diagnosis, “after 12 years of not understanding each other, I started to see that he couldn’t help his behaviour. He wasn’t a bad person.”

There isn’t a figure for the number of adults diagnosed as being on the autism spectrum each year but, anecdotally, it is on the rise. More than 1% of the population has autism, so there will be many adults who suspect or are unaware that they have the condition – and many who will be in relationships with people considered neurotypical. For many people, it is picked up if their child is diagnosed, as was the case with David (there is thought to be a hereditary aspect). But another common pathway is if their partner suspects ASD and encourages them to look into it.

Laura James … ‘Autistic women tend to be quite straightforward and honest.’ Photograph: Tim James

It is by no means a certainty that a relationship between someone with ASD and someone without will be difficult – every person with ASD is different, as is every relationship. But a diagnosis can come as a relief for both partners.

Before he was diagnosed last year at the age of 30, Robert (not his real name) says his wife referred to him “as having ‘quirks’ – such as wearing earplugs all the time or needing to sit next to walls, or with my back to them. I have since become aware that she makes an effort to help me with these things such as finding suitable tables in coffee shops or making sure I can sit at the back of a bus so nobody can sit behind me.”

The diagnosis has made sense of a lot of his life, he says. “I find it very hard to maintain relationships with other people. I have no social circle, although I do find that social media helps me interact with people I would normally struggle with. I felt immensely guilty that I didn’t have those relationships – and more guilty for not really being bothered that I didn’t have them. Receiving a diagnosis has taught me that it’s OK.”

It has also helped explain some of his actions to his wife. “I have become acutely aware of how obsessed I become over things, something that has caused issues with my wife. She understands now that sometimes it’s easier just to let them run their course.”

There are still misunderstandings, though. Robert has depression, which led to him leaving his job at a local authority. His wife, he says, “doesn’t understand that I forget to take medication, I struggle ringing people [to seek help], and, when I do get to speak to people, I can’t articulate myself, so I’m not able to get the help I want or need. That causes a huge amount of stress between us.”

“One of the characteristics of ASD can be [that the person has] two characters,” says Tony Attwood, a clinical psychologist and expert on Asperger syndrome. “They are able to socialise in a work environment, but it’s very arduous and exhausting. When they come home, they want isolation to recover, or to recover by engaging in their special interest – but their partner often feels left out of their life.”

Generalisations only go so far, but Attwood says he has seen common themes in the conflicts that can occur. “The person with autism may not read the signals when their partner needs affection, consoling or compassion, and may not respond as anticipated, which then leads the neurotypical person feeling that the other person may not care. They do care, but they’re not good at reading the signals.” The partner with ASD, meanwhile, may “need less frequent and intense expressions of affection. There may be an imbalance in the relationship between what one partner needs and what the other is expected to give.” Attwood says he recently asked a couple for their definition of “love”. The husband, who was on the spectrum, “thought for 10 or 20 seconds and said ‘loyalty’, which is an appropriate expression of love. But his partner was looking for more passion.”

Again, it is a generalisation, but Attwood says partners with ASD tend to be loyal and honest. “The person is very kind in many ways and very caring, but may have a different way of showing it.” A 2010 study published in the British Journal of Special Education (and referred to by the National Autistic Society) interviewed young autistic people and found that many said that, when they were younger, they would have benefited from more education about how relationships work. More recently, a 2017 Swedish study found that one out of five individuals with autistic traits felt they did not fit accepted labels for sexual orientation; they were also more likely to identify as bisexual than individuals without autistic traits. Advocates said the study showed the need to hear more from autistic people about their experience of sexual identity, and to be open to more diverse interpretations of it.

Amy Schumer … talked about her husband’s diagnosis. Photograph: Elizabeth Sisson/Netflix

In March, the comedian Amy Schumer talked about her husband, Chris Fischer, and his ASD diagnosis, in her Netflix standup special. “All the characteristics that make it clear that he is on the spectrum are all of the reasons that I fell madly in love with him,” she says in her show. “He says whatever is on his mind. He keeps it so real. He doesn’t care about social norms, or what you expect him to say or do … he can’t lie. Is that the dream man?” Interviewed later about his diagnosis, she said: “It has been totally positive … The tools that we have been given have made his life so much better and our marriage and our life more manageable, so I just wanted to encourage people to not be afraid of that stigma.”

Many relationships are long and happy, says Attwood – “but often, there have been adjustments to what to expect in the relationship”. Counselling can help with this, but only if the counsellor has experience of dealing with autism. There are also organisations, such as Different Together, to support partners of those with Asperger’s.

“I actually think there’s an argument that autistic women are really great when married to neurotypical men,” says Laura James, the author of Odd Girl Out, a memoir about being diagnosed with ASD in her 40s, and an ambassador for the National Autistic Society. “Men in relationships often say: ‘I don’t know what my wife wants me to say’ or ‘If I upset her, she says everything is fine when I know it’s not.’ Autistic women tend to be – although I can’t speak for everyone – quite straightforward and honest. When I was in the dating stage of my life, if I fancied someone, I’d tell them, whereas everybody else was playing games.” Equally, she says, she isn’t offended by her neurotypical husband’s straight talking.

She says she is not “the most romantic person”, which has not been an issue in her marriage, but probably was in previous relationships. “I think it caused problems when I was younger … boyfriends dumped me because they thought I didn’t like them.” Her diagnosis has helped her and her husband to understand her behaviour. In situations, such as in hospital or on a plane, where there was simultaneously a sensory overload and a lack of control, “I would have epic meltdowns” – once she almost grounded a flight because of it. “I think it was a little tiresome for him when he didn’t have any idea about why I would be behaving like that.”

And she hasn’t ever been able to engage in arguments, she says. “He has had to adapt that behaviour. Rather than getting very angry about something, he has learned to sit down and say: ‘This doesn’t really work for me,’ and I’m able to respond to that.”

Karen and David now do things differently to make sure everybody is happy. Karen says he is more open and trusting now. “For a long time, he thought he was, in his words, ‘broken’, but he didn’t want to let on to the world, or to me because he thought I might reject him.”

Other changes they have made include not sitting down to meals together – which can be too stressful for David and their two children, both of whom have been diagnosed with ASD – and favouring planning over spontaneity. “We have proved that, with hard work and understanding, you can get there,” says Karen.