In the 1970s, Joni Mitchell was reaching out, taking it all in. The shy girl and the party girl did a little boho dance inside her, trading places depending on what day it was. "I'm always talkin', chicken squawkin', bigawwk, bigAWWWK!" she yakked in Talk to Me, musicalising the women's art of conversation as it goes off the rails. That song, from Don Juan's Reckless Daughter, is an extrovert's embarrassing indulgence, the final shove from a pushy broad. Mitchell liked to run her mouth off. But then she would retreat into solitude. Reflecting on this period later, she'd describe the 1970s as a time when she moved away from the introversion that had reached its nearly claustrophobic peak on Blue and toward a new role as an observer, telling others' stories as she encountered them on the road. Yet in another, fundamental way, she remained inwardly focused. She just had a different framework for doing so, one emblematic of the time. A silent listener sits across from her in Hejira's songs as she recounts her excursions. Herself, in the role of analyst.

"I tried to run away myself," Mitchell sings in Coyote, "to run away and wrestle with my ego." Hejira's opening salvo identifies her travels as both geographical and psychological. She ranges through her own mind as much as anywhere else, but her lyrics show signs of a new mindset. The scholar David Shumway identified the Freudian couch as the source. "Ambivalence is a characteristic of neurotic states, but it is also a product of the work of analysis," he wrote in his book Rock Star. "Mitchell's work depends heavily on the discourse of, if not psychoanalysis proper, then the therapy of the talking cure in a general sense."

Bringing psychoanalysis into the conversation explains so much, not only about Mitchell's 1970s preoccupations, but about the looping, overflowing structure of her songs as the decade progressed. I wasn't surprised to discover that Mitchell's own experiences with therapy were at best mixed. In 1973, bereft after a brief fractured romance with Jackson Browne, she started seeing Dr Martin Grotjahn on Warren Beatty's recommendation. Mitchell dove in but soon decided she could do the job better herself. Pretty soon, references to analysis started slipping into her work: Court and Spark includes both the haunting portrait of an unstable patient, Trouble Child, and the analysand's retort, Twisted. From then on, therapy's terminology turned up in her lyrics again and again.

This was not unusual in the "me" decade, as some dubbed the 1970s - everybody had a shrink and a stack of self-help paperbacks and talked that jargon with the ease and enthusiasm of the newly enlightened. Mitchell managed something unique, though. She remade the song form to reveal her inner journeys.

As she sped along the highways of a US increasingly turned on to its own navel, Mitchell's compositions became as evocative of that historical moment's ideas about self-actualisation as they were of the changing landscapes outside her vehicle windows. Her conversational vocal style became a means for embodying rumination. To accommodate her intuitive writing style, she abandoned hooks and clear refrains in favour of soliloquies and sonic meltdowns, all serving insights that paid off without resolving.

"An artist needs a certain amount of turmoil and confusion and I've created out of that, even severe depression," she told a reporter in 1974, explaining why she started therapy. "But I had a lot of questions about myself, the way I was conducting my lives ... what were my values in this time." I imagine her keeping two notebooks, marked up in different inks for every town through which she passed - one recording details about landmarks, people, incidents; the other devoted to moods, memories, the ghosts she carried around with her. A meditation teacher would call it the monkey mind, always slapping away the serenity of concentration and insight. A gestalt therapist might say: "Joni, you're talking to an empty chair; that technique employed such metaphors to help people process life's half-completed conversations." A shaman might hear her free-associating and decide she's on a vision quest.

Mitchell's psychic trips took many forms. I'm pretty sure she tried psychedelics, given her interest in spiritual seekers who embraced the practice; she was a devoted fan of the anthropologist Carlos Castaneda, whose shamanic training manuals touted the wonders of peyote. She definitely got into transcendental meditation - her name appears in several different 1970s gossip columns among the countless celebs who paid the Maharishi for their mantras. She did yoga, though she never went macrobiotic, enjoying hot dogs too much.

With the language of psychotherapy permeating everything from novels (Erica Jong's Fear of Flying) to films (Annie Hall) to prime-time sitcoms (The Bob Newhart Show), music followed suit. Male rockers incorporated tales of madness into their lexicon of questing heroes, from Elton John's Madman Across the Water to Pink Floyd's Brain Damage. Women rarely explored the subject in the same way, and the exceptions were marketed as pop novelties. I loved these songs. Their main avatar was the preternaturally calm Australian singer Helen Reddy, who counted several portraits of madwomen among her many hits. My favourite was Angie Baby, an account of teen breakdown in which music itself drove its poor heroine over the edge. I valued this song because its mad girl turned out to not be crazy after all. Her radio really did have magic powers. It allowed her to imprison a neighbour boy who had broken into her house "with evil on his mind", upending his plan to assault her and turning him into the "secret lover who keeps her satisfied". I always sang the song's punch line at the top of my lungs: "It's so nice to be insane. No one asks you to explain!"

I didn't discover the one woman who openly explored her own breakdown and recovery in song until I was well on Mitchell's path, looking around for others who took risks the way she did. Dory Previn didn't sell a lot of records, though her story certainly made the tabloids. She had found her place among the Laurel Canyon - adjacent elite, partnering with her husband, André, on film soundtracks and theme songs such as the wistful theme from Valley of the Dolls, a movie about - what else? - women having breakdowns. Their partnership imploded when André took up with Previn's friend Mia Farrow, 20 years her junior, who, in the lyricist's own cutting words, had "admired my unmade bed". Previn's subsequent collapse on a cross-country flight landed her in a psychiatric hospital - not that uncommon a fate for well-off women who weren't coping well with calamitous life changes. But Previn didn't keep mum about the experience afterward; in fact, she did the opposite, recording her brutal, brilliant album On My Way to Where.

That song cycle relates the story of her husband's betrayal and her derangement with a clarity rarely matched by other songwriters. Previn talked openly of writing these songs as "self-prescribed hospital therapy". She told the Los Angeles Times: "I had said it, lived it, screamed it, but still I was afraid of dealing with my background. There was nothing to do but set it down on paper. I had to get my demons in the open and say, 'OK, I have to live with you, so let's hassle it out.'" The sound of Previn hassling it out is unlike anything else recorded in those years. She went even further than Mitchell in creating sometimes monstrous, all-too-human characters in her songs. But her combination of musical-comedy razzmatazz and psychoanalysis-inspired inquiries only resonated with a small cult of listeners. Letting it all hang out had its limits when it came to being a pop star.

Mitchell figured out how to balance self-exposure and a sense of mystery more effectively. Her songs invoking psychotherapy and other vision quests are sometimes humorous, often sceptical, never conclusive. Mystery remained attractive to her, as did the safety net of occasional discretion. "I am returning to myself / These things that you and I suppressed," she sings on Hejira's title track. But this homecoming wouldn't be simple or direct.

In her essay on Mitchell, Anne Hilker calls Amelia the best example of Mitchell's grounding in melancholy - a Freudian term not simply synonymous with sadness but denoting the unresolved losses that afflict and divide a person's psyche. Musically and lyrically, Hilker writes, the song "gestures toward perpetual movement". It wavers between two keys, F major and G major; its suspended chords, with their built-in dissonance, reinforce its sense of exile, as does the circular structure, never offering the climax of a bridge or a chorus. Plus, the song is a riddle: its refrain, "Amelia, it was just a false alarm", is never explained. Is the false alarm a reference to the famous aviator Amelia Earhart, her body never recovered from a crash no one saw? Might Mitchell be speculating on the moment the plane went down, a fault in the wiring that ended Earhart's legendary restless life? Or could the false alarm be plaguing Mitchell herself, as she sets out for places unknown within her own subconscious, surveying patterns built from memories and impulses that she only partly understands?

Amelia is one of two songs on Hejira that doesn't have a bass line, another reason it feels ethereal, ungrounded. This album foregrounds Mitchell's sonic twinship with Jaco Pastorius; his bass playing, overdubbed after her parts on the album were completed, answers her voice and guitar so intuitively that they seem like extensions of her own thoughts. I think about Pastorius as another voice inside Mitchell's own head. The bass is an instrument of rumination, but also of insight. I've sometimes wondered: why turn him up so high? But I think he provided the final element of unrest that realised Mitchell's goal of replicating an inner life in a way that conventional songcraft, with its neater harmonies and resolutions, could not. And sometimes those bass parts push her questioning to a whole new level.

By her next album, 1977's Don Juan's Reckless Daughter, Mitchell was leaning out of the psyche's language and into mysticism. Pastorius was with her. The record's great psychedelic moment is the song suite Paprika Plains, but plenty of other examples of vision questing surface on this complicated, truly over-the-top recording. The album's very title, though seeming to poke fun at Mitchell's status as a female Casanova, also expresses her appreciation for Castaneda's Don Juan books, fictionalised accounts of his hallucinatory journeys with a Yaqui shaman. The "split-tongued" spirit Mitchell conjures in the title track, whose dual nature - world-bound serpent and transcendent eagle - presides over these songs, is exactly the kind of guide Castaneda continually evoked in his bestselling books.

It makes sense that Mitchell's inner journeys would get more psychedelic as the 1970s wore on. By 1977 she had moved past psychoanalysis through various forms of meditation, trading in a cocaine habit acquired on the road for more organic routes toward enlightenment. Urged by guitarist Robben Ford's wife to seek out the guidance of the Tibetan sage Chögyam Trungpa Rinpoche - a guru as popular among Hollywood habitués as the psychoanalyst Grotjahn had once been - Mitchell had a confrontational encounter with the monk that, according to her, put her into a three-day state of what Buddhists call satori, or no-mind. "I left his office and for three days I was in an awakened state," she said in 2005. "The technique completely silenced that thing, the loud, little noisy radio station that stands between you and the great mind."

That major reset tipped Mitchell's writing more toward the mystical. With this turn, she was again in step with American culture. Overshadowed by the medicalisation of mental health and the mainstreaming of New Age self-help movements, psychotherapy remained an important tool and Freud's talking cure a historical touchstone, but no longer was it a definitive force within Americans' understanding of their inner lives. But Mitchell would continue to look within and sometimes use Freud's language to do so. "I can't quit analysing; I'm an artist," she had told Rinpoche before he zapped her with his breathing technique.